diff --git a/asminc/rp6502.inc b/asminc/rp6502.inc
new file mode 100644
index 000000000..3fa493331
--- /dev/null
+++ b/asminc/rp6502.inc
@@ -0,0 +1,101 @@
+; Copyright (c) 2023 Rumbledethumps
+;
+; SPDX-License-Identifier: Zlib
+; SPDX-License-Identifier: BSD-3-Clause
+; SPDX-License-Identifier: Unlicense
+
+; RIA UART
+RIA_READY       := $FFE0 ; TX=$80 RX=$40
+RIA_TX          := $FFE1
+RIA_RX          := $FFE2
+
+; VSYNC from PIX VGA
+RIA_VSYNC       := $FFE3
+
+; RIA XRAM portal 0
+RIA_RW0         := $FFE4
+RIA_STEP0       := $FFE5
+RIA_ADDR0       := $FFE6
+
+; RIA XRAM portal 1
+RIA_RW1         := $FFE8
+RIA_STEP1       := $FFE9
+RIA_ADDR1       := $FFEA
+
+; RIA OS fastcall
+RIA_XSTACK      := $FFEC
+RIA_ERRNO       := $FFED
+RIA_OP          := $FFEF
+RIA_IRQ         := $FFF0
+RIA_SPIN        := $FFF1
+RIA_BUSY        := $FFF2 ; Bit $80
+RIA_A           := $FFF4
+RIA_X           := $FFF6
+RIA_SREG        := $FFF8
+
+; RIA OS operation numbers
+RIA_OP_EXIT               := $FF
+RIA_OP_ZXSTACK            := $00
+RIA_OP_XREG               := $01
+RIA_OP_PHI2               := $02
+RIA_OP_CODEPAGE           := $03
+RIA_OP_LRAND              := $04
+RIA_OP_STDIN_OPT          := $05
+RIA_OP_CLOCK_GETRES       := $10
+RIA_OP_CLOCK_GETTIME      := $11
+RIA_OP_CLOCK_SETTIME      := $12
+RIA_OP_CLOCK_GETTIMEZONE  := $13
+RIA_OP_OPEN               := $14
+RIA_OP_CLOSE              := $15
+RIA_OP_READ_XSTACK        := $16
+RIA_OP_READ_XRAM          := $17
+RIA_OP_WRITE_XSTACK       := $18
+RIA_OP_WRITE_XRAM         := $19
+RIA_OP_LSEEK              := $1A
+RIA_OP_UNLINK             := $1B
+RIA_OP_RENAME             := $1C
+
+; 6522 VIA
+VIA             := $FFD0        ; VIA base address
+VIA_PB          := VIA+$0       ; Port register B
+VIA_PA1         := VIA+$1       ; Port register A
+VIA_PRB         := VIA+$0       ; *** Deprecated ***
+VIA_PRA         := VIA+$1       ; *** Deprecated ***
+VIA_DDRB        := VIA+$2       ; Data direction register B
+VIA_DDRA        := VIA+$3       ; Data direction register A
+VIA_T1CL        := VIA+$4       ; Timer 1, low byte
+VIA_T1CH        := VIA+$5       ; Timer 1, high byte
+VIA_T1LL        := VIA+$6       ; Timer 1 latch, low byte
+VIA_T1LH        := VIA+$7       ; Timer 1 latch, high byte
+VIA_T2CL        := VIA+$8       ; Timer 2, low byte
+VIA_T2CH        := VIA+$9       ; Timer 2, high byte
+VIA_SR          := VIA+$A       ; Shift register
+VIA_CR          := VIA+$B       ; Auxiliary control register
+VIA_PCR         := VIA+$C       ; Peripheral control register
+VIA_IFR         := VIA+$D       ; Interrupt flag register
+VIA_IER         := VIA+$E       ; Interrupt enable register
+VIA_PA2         := VIA+$F       ; Port register A w/o handshake
+
+; Values in ___oserror are the union of these FatFs errors and errno.inc
+.enum
+    FR_OK = 32             ; Succeeded
+    FR_DISK_ERR            ; A hard error occurred in the low level disk I/O layer
+    FR_INT_ERR             ; Assertion failed
+    FR_NOT_READY           ; The physical drive cannot work
+    FR_NO_FILE             ; Could not find the file
+    FR_NO_PATH             ; Could not find the path
+    FR_INVALID_NAME        ; The path name format is invalid
+    FR_DENIED              ; Access denied due to prohibited access or directory full
+    FR_EXIST               ; Access denied due to prohibited access
+    FR_INVALID_OBJECT      ; The file/directory object is invalid
+    FR_WRITE_PROTECTED     ; The physical drive is write protected
+    FR_INVALID_DRIVE       ; The logical drive number is invalid
+    FR_NOT_ENABLED         ; The volume has no work area
+    FR_NO_FILESYSTEM       ; There is no valid FAT volume
+    FR_MKFS_ABORTED        ; The f_mkfs() aborted due to any problem
+    FR_TIMEOUT             ; Could not get a grant to access the volume within defined period
+    FR_LOCKED              ; The operation is rejected according to the file sharing policy
+    FR_NOT_ENOUGH_CORE     ; LFN working buffer could not be allocated
+    FR_TOO_MANY_OPEN_FILES ; Number of open files > FF_FS_LOCK
+    FR_INVALID_PARAMETER   ; Given parameter is invalid
+.endenum
diff --git a/cfg/rp6502.cfg b/cfg/rp6502.cfg
new file mode 100644
index 000000000..a3e3b29ce
--- /dev/null
+++ b/cfg/rp6502.cfg
@@ -0,0 +1,42 @@
+#
+# Copyright (c) 2023 Rumbledethumps
+#
+# SPDX-License-Identifier: Zlib
+# SPDX-License-Identifier: BSD-3-Clause
+# SPDX-License-Identifier: Unlicense
+#
+
+SYMBOLS {
+    __STARTUP__:   type = import;
+    __STACKSIZE__: type = weak, value = $0800;
+}
+MEMORY {
+    ZP:       file = "", define = yes, start = $0000, size = $0100;
+    CPUSTACK: file = "",               start = $0100, size = $0100;
+    RAM:      file = %O, define = yes, start = $0200, size = $FD00 - __STACKSIZE__;
+}
+SEGMENTS {
+    ZEROPAGE: load = ZP,     type = zp;
+    STARTUP:  load = RAM,    type = ro;
+    LOWCODE:  load = RAM,    type = ro,  optional = yes;
+    ONCE:     load = RAM,    type = ro,  optional = yes;
+    CODE:     load = RAM,    type = ro;
+    RODATA:   load = RAM,    type = ro;
+    DATA:     load = RAM,    type = rw,  define   = yes;
+    BSS:      load = RAM,    type = bss, define   = yes;
+}
+FEATURES {
+    CONDES: type    = constructor,
+            label   = __CONSTRUCTOR_TABLE__,
+            count   = __CONSTRUCTOR_COUNT__,
+            segment = ONCE;
+    CONDES: type    = destructor,
+            label   = __DESTRUCTOR_TABLE__,
+            count   = __DESTRUCTOR_COUNT__,
+            segment = RODATA;
+    CONDES: type    = interruptor,
+            label   = __INTERRUPTOR_TABLE__,
+            count   = __INTERRUPTOR_COUNT__,
+            segment = RODATA,
+            import  = __CALLIRQ__;
+}
diff --git a/include/rp6502.h b/include/rp6502.h
new file mode 100644
index 000000000..0c2ba3881
--- /dev/null
+++ b/include/rp6502.h
@@ -0,0 +1,246 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#ifndef _RP6502_H
+#define _RP6502_H
+
+/* RP6502 VIA $FFD0-$FFDF */
+
+#include <_6522.h>
+#define VIA (*(volatile struct __6522 *)0xFFD0)
+
+/* RP6502 RIA $FFE0-$FFF9 */
+
+struct __RP6502
+{
+    const unsigned char ready;
+    unsigned char tx;
+    const unsigned char rx;
+    const unsigned char vsync;
+    unsigned char rw0;
+    unsigned char step0;
+    unsigned int addr0;
+    unsigned char rw1;
+    unsigned char step1;
+    unsigned int addr1;
+    unsigned char xstack;
+    unsigned char errno_lo;
+    unsigned char errno_hi;
+    unsigned char op;
+    unsigned char irq;
+    const unsigned char spin;
+    const unsigned char busy;
+    const unsigned char lda;
+    unsigned char a;
+    const unsigned char ldx;
+    unsigned char x;
+    const unsigned char rts;
+    unsigned int sreg;
+};
+#define RIA (*(volatile struct __RP6502 *)0xFFE0)
+
+#define RIA_READY_TX_BIT 0x80
+#define RIA_READY_RX_BIT 0x40
+#define RIA_BUSY_BIT 0x80
+
+/* XSTACK helpers */
+
+void __fastcall__ ria_push_long(unsigned long val);
+void __fastcall__ ria_push_int(unsigned int val);
+#define ria_push_char(v) RIA.xstack = v
+
+long __fastcall__ ria_pop_long(void);
+int __fastcall__ ria_pop_int(void);
+#define ria_pop_char() RIA.xstack
+
+/* Set the RIA fastcall register */
+
+void __fastcall__ ria_set_axsreg(unsigned long axsreg);
+void __fastcall__ ria_set_ax(unsigned int ax);
+#define ria_set_a(v) RIA.a = v
+
+/* Run an OS operation */
+
+int __fastcall__ ria_call_int(unsigned char op);
+long __fastcall__ ria_call_long(unsigned char op);
+
+/* These run _mappederrno() on error */
+
+int __fastcall__ ria_call_int_errno(unsigned char op);
+long __fastcall__ ria_call_long_errno(unsigned char op);
+
+/* OS operation numbers */
+
+#define RIA_OP_EXIT 0xFF
+#define RIA_OP_ZXSTACK 0x00
+#define RIA_OP_XREG 0x01
+#define RIA_OP_PHI2 0x02
+#define RIA_OP_CODEPAGE 0x03
+#define RIA_OP_LRAND 0x04
+#define RIA_OP_STDIN_OPT 0x05
+#define RIA_OP_CLOCK_GETRES 0x10
+#define RIA_OP_CLOCK_GETTIME 0x11
+#define RIA_OP_CLOCK_SETTIME 0x12
+#define RIA_OP_CLOCK_GETTIMEZONE 0x13
+#define RIA_OP_OPEN 0x14
+#define RIA_OP_CLOSE 0x15
+#define RIA_OP_READ_XSTACK 0x16
+#define RIA_OP_READ_XRAM 0x17
+#define RIA_OP_WRITE_XSTACK 0x18
+#define RIA_OP_WRITE_XRAM 0x19
+#define RIA_OP_LSEEK 0x1A
+#define RIA_OP_UNLINK 0x1B
+#define RIA_OP_RENAME 0x1C
+
+/* C API for the operating system. */
+
+int __cdecl__ xreg(char device, char channel, unsigned char address, ...);
+int __fastcall__ phi2(void);
+int __fastcall__ codepage(void);
+long __fastcall__ lrand(void);
+int __fastcall__ stdin_opt(unsigned long ctrl_bits, unsigned char str_length);
+int __fastcall__ read_xstack(void *buf, unsigned count, int fildes);
+int __fastcall__ read_xram(unsigned buf, unsigned count, int fildes);
+int __fastcall__ write_xstack(const void *buf, unsigned count, int fildes);
+int __fastcall__ write_xram(unsigned buf, unsigned count, int fildes);
+
+/* XREG location helpers */
+
+#define xreg_ria_keyboard(...) xreg(0, 0, 0, __VA_ARGS__)
+#define xreg_ria_mouse(...) xreg(0, 0, 1, __VA_ARGS__)
+#define xreg_vga_canvas(...) xreg(1, 0, 0, __VA_ARGS__)
+#define xreg_vga_mode(...) xreg(1, 0, 1, __VA_ARGS__)
+
+/* XRAM structure helpers */
+
+#define xram0_struct_set(addr, type, member, val)                  \
+    RIA.addr0 = (unsigned)(&((type *)0)->member) + (unsigned)addr; \
+    switch (sizeof(((type *)0)->member))                           \
+    {                                                              \
+    case 1:                                                        \
+        RIA.rw0 = val;                                             \
+        break;                                                     \
+    case 2:                                                        \
+        RIA.step0 = 1;                                             \
+        RIA.rw0 = val & 0xff;                                      \
+        RIA.rw0 = (val >> 8) & 0xff;                               \
+        break;                                                     \
+    case 4:                                                        \
+        RIA.step0 = 1;                                             \
+        RIA.rw0 = (unsigned long)val & 0xff;                       \
+        RIA.rw0 = ((unsigned long)val >> 8) & 0xff;                \
+        RIA.rw0 = ((unsigned long)val >> 16) & 0xff;               \
+        RIA.rw0 = ((unsigned long)val >> 24) & 0xff;               \
+        break;                                                     \
+    }
+
+#define xram1_struct_set(addr, type, member, val)                  \
+    RIA.addr1 = (unsigned)(&((type *)0)->member) + (unsigned)addr; \
+    switch (sizeof(((type *)0)->member))                           \
+    {                                                              \
+    case 1:                                                        \
+        RIA.rw1 = val;                                             \
+        break;                                                     \
+    case 2:                                                        \
+        RIA.step1 = 1;                                             \
+        RIA.rw1 = val & 0xff;                                      \
+        RIA.rw1 = (val >> 8) & 0xff;                               \
+        break;                                                     \
+    case 4:                                                        \
+        RIA.step1 = 1;                                             \
+        RIA.rw1 = (unsigned long)val & 0xff;                       \
+        RIA.rw1 = ((unsigned long)val >> 8) & 0xff;                \
+        RIA.rw1 = ((unsigned long)val >> 16) & 0xff;               \
+        RIA.rw1 = ((unsigned long)val >> 24) & 0xff;               \
+        break;                                                     \
+    }
+
+typedef struct
+{
+    unsigned char x_wrap; // bool
+    unsigned char y_wrap; // bool
+    int x_pos_px;
+    int y_pos_px;
+    int width_chars;
+    int height_chars;
+    unsigned xram_data_ptr;
+    unsigned xram_palette_ptr;
+    unsigned xram_font_ptr;
+} vga_mode1_config_t;
+
+typedef struct
+{
+    unsigned char x_wrap; // bool
+    unsigned char y_wrap; // bool
+    int x_pos_px;
+    int y_pos_px;
+    int width_tiles;
+    int height_tiles;
+    unsigned xram_data_ptr;
+    unsigned xram_palette_ptr;
+    unsigned xram_tile_ptr;
+} vga_mode2_config_t;
+
+typedef struct
+{
+    unsigned char x_wrap; // bool
+    unsigned char y_wrap; // bool
+    int x_pos_px;
+    int y_pos_px;
+    int width_px;
+    int height_px;
+    unsigned xram_data_ptr;
+    unsigned xram_palette_ptr;
+} vga_mode3_config_t;
+
+typedef struct
+{
+    int x_pos_px;
+    int y_pos_px;
+    unsigned xram_sprite_ptr;
+    unsigned char log_size;
+    unsigned char has_opacity_metadata; // bool
+} vga_mode4_sprite_t;
+
+typedef struct
+{
+    int transform[6];
+    int x_pos_px;
+    int y_pos_px;
+    unsigned xram_sprite_ptr;
+    unsigned char log_size;
+    unsigned char has_opacity_metadata; // bool
+} vga_mode4_asprite_t;
+
+/* Values in __oserror are the union of these FatFs errors and errno.h */
+
+typedef enum
+{
+    FR_OK = 32,             /* Succeeded */
+    FR_DISK_ERR,            /* A hard error occurred in the low level disk I/O layer */
+    FR_INT_ERR,             /* Assertion failed */
+    FR_NOT_READY,           /* The physical drive cannot work */
+    FR_NO_FILE,             /* Could not find the file */
+    FR_NO_PATH,             /* Could not find the path */
+    FR_INVALID_NAME,        /* The path name format is invalid */
+    FR_DENIED,              /* Access denied due to prohibited access or directory full */
+    FR_EXIST,               /* Access denied due to prohibited access */
+    FR_INVALID_OBJECT,      /* The file/directory object is invalid */
+    FR_WRITE_PROTECTED,     /* The physical drive is write protected */
+    FR_INVALID_DRIVE,       /* The logical drive number is invalid */
+    FR_NOT_ENABLED,         /* The volume has no work area */
+    FR_NO_FILESYSTEM,       /* There is no valid FAT volume */
+    FR_MKFS_ABORTED,        /* The f_mkfs() aborted due to any problem */
+    FR_TIMEOUT,             /* Could not get a grant to access the volume within defined period */
+    FR_LOCKED,              /* The operation is rejected according to the file sharing policy */
+    FR_NOT_ENOUGH_CORE,     /* LFN working buffer could not be allocated */
+    FR_TOO_MANY_OPEN_FILES, /* Number of open files > FF_FS_LOCK */
+    FR_INVALID_PARAMETER    /* Given parameter is invalid */
+} FRESULT;
+
+#endif /* _RP6502_H */
diff --git a/libsrc/Makefile b/libsrc/Makefile
index cf7389d51..8a4f11414 100644
--- a/libsrc/Makefile
+++ b/libsrc/Makefile
@@ -33,6 +33,7 @@ TARGETS = apple2       \
           none         \
           osic1p       \
           pce          \
+          rp6502       \
           sim6502      \
           sim65c02     \
           supervision  \
diff --git a/libsrc/rp6502/close.c b/libsrc/rp6502/close.c
new file mode 100644
index 000000000..1fdc40545
--- /dev/null
+++ b/libsrc/rp6502/close.c
@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+#include <errno.h>
+
+int __fastcall__ close(int fd)
+{
+    ria_set_ax(fd);
+    return ria_call_int_errno(RIA_OP_CLOSE);
+}
diff --git a/libsrc/rp6502/codepage.c b/libsrc/rp6502/codepage.c
new file mode 100644
index 000000000..c0914651d
--- /dev/null
+++ b/libsrc/rp6502/codepage.c
@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+
+int __fastcall__ codepage(void)
+{
+    return ria_call_int(RIA_OP_CODEPAGE);
+}
diff --git a/libsrc/rp6502/crt0.s b/libsrc/rp6502/crt0.s
new file mode 100644
index 000000000..e6406fe5e
--- /dev/null
+++ b/libsrc/rp6502/crt0.s
@@ -0,0 +1,54 @@
+; Copyright (c) 2023 Rumbledethumps
+;
+; SPDX-License-Identifier: Zlib
+; SPDX-License-Identifier: BSD-3-Clause
+; SPDX-License-Identifier: Unlicense
+
+; Boilerplate crt0.s
+
+.export _init, _exit
+.import _main
+
+.export __STARTUP__ : absolute = 1
+.import __RAM_START__, __RAM_SIZE__
+
+.import copydata, zerobss, initlib, donelib
+
+.include "rp6502.inc"
+.include "zeropage.inc"
+
+.segment  "STARTUP"
+
+; Essential 6502 startup the CPU doesn't do
+_init:
+    ldx #$FF
+    txs
+    cld
+
+; Set cc65 argument stack pointer
+    lda #<(__RAM_START__ + __RAM_SIZE__)
+    sta sp
+    lda #>(__RAM_START__ + __RAM_SIZE__)
+    sta sp+1
+
+; Initialize memory storage
+    jsr zerobss   ; Clear BSS segment
+    jsr copydata  ; Initialize DATA segment
+    jsr initlib   ; Run constructors
+
+; Call main()
+    jsr _main
+
+; Back from main() also the _exit entry
+; Stack the exit value in case destructors call OS
+_exit:
+    phx
+    pha
+    jsr donelib  ; Run destructors
+    pla
+    sta RIA_A
+    plx
+    stx RIA_X
+    lda #$FF     ; exit()
+    sta RIA_OP
+    stp
diff --git a/libsrc/rp6502/getres.c b/libsrc/rp6502/getres.c
new file mode 100644
index 000000000..c60bbd38d
--- /dev/null
+++ b/libsrc/rp6502/getres.c
@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+#include <time.h>
+
+extern int __clock_gettimespec(struct timespec *ts, unsigned char op);
+
+int clock_getres(clockid_t clock_id, struct timespec *res)
+{
+    ria_set_ax(clock_id);
+    return __clock_gettimespec(res, RIA_OP_CLOCK_GETRES);
+}
diff --git a/libsrc/rp6502/gettime.c b/libsrc/rp6502/gettime.c
new file mode 100644
index 000000000..b40615e9e
--- /dev/null
+++ b/libsrc/rp6502/gettime.c
@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+#include <time.h>
+
+extern int __clock_gettimespec(struct timespec *ts, unsigned char op);
+
+int clock_gettime(clockid_t clock_id, struct timespec *tp)
+{
+    (void)clock_id;
+    /* time.s doesn't set the stack value for clock_id (bug?) */
+    ria_set_ax(CLOCK_REALTIME);
+    return __clock_gettimespec(tp, RIA_OP_CLOCK_GETTIME);
+}
diff --git a/libsrc/rp6502/gettimespec.c b/libsrc/rp6502/gettimespec.c
new file mode 100644
index 000000000..ef136c6fe
--- /dev/null
+++ b/libsrc/rp6502/gettimespec.c
@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+#include <time.h>
+
+int __clock_gettimespec(struct timespec *ts, unsigned char op)
+/* Internal method shared by clock_getres and clock_gettime. */
+{
+    int ax = ria_call_int_errno(op);
+    if (ax >= 0)
+    {
+        ts->tv_sec = ria_pop_long();
+        ts->tv_nsec = ria_pop_long();
+    }
+    return ax;
+}
diff --git a/libsrc/rp6502/gettimezone.c b/libsrc/rp6502/gettimezone.c
new file mode 100644
index 000000000..db9060967
--- /dev/null
+++ b/libsrc/rp6502/gettimezone.c
@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+#include <time.h>
+
+int clock_gettimezone(clockid_t clock_id, struct _timezone *tz)
+{
+    int ax;
+    ria_set_ax(clock_id);
+    ax = ria_call_int_errno(RIA_OP_CLOCK_GETTIMEZONE);
+    if (ax >= 0)
+    {
+        char i;
+        for (i = 0; i < sizeof(struct _timezone); i++)
+            ((char *)tz)[i] = ria_pop_char();
+    }
+    return ax;
+}
diff --git a/libsrc/rp6502/initenv.s b/libsrc/rp6502/initenv.s
new file mode 100644
index 000000000..b6546e320
--- /dev/null
+++ b/libsrc/rp6502/initenv.s
@@ -0,0 +1,16 @@
+; Copyright (c) 2023 Rumbledethumps
+;
+; SPDX-License-Identifier: Zlib
+; SPDX-License-Identifier: BSD-3-Clause
+; SPDX-License-Identifier: Unlicense
+
+.constructor initenv, 24
+.import __environ, __envcount, __envsize
+
+.segment "ONCE"
+
+.proc initenv
+
+    rts
+
+.endproc
diff --git a/libsrc/rp6502/irq.s b/libsrc/rp6502/irq.s
new file mode 100644
index 000000000..ffc152aac
--- /dev/null
+++ b/libsrc/rp6502/irq.s
@@ -0,0 +1,51 @@
+; Copyright (c) 2023 Rumbledethumps
+;
+; SPDX-License-Identifier: Zlib
+; SPDX-License-Identifier: BSD-3-Clause
+; SPDX-License-Identifier: Unlicense
+
+.export initirq, doneirq
+.import callirq, _exit
+
+.include "rp6502.inc"
+
+.segment "ONCE"
+
+initirq:
+    lda #<handler
+    ldx #>handler
+    sei
+    sta $FFFE
+    stx $FFFF
+    cli
+    rts
+
+.code
+
+doneirq:
+    sei
+    rts
+
+.segment "LOWCODE"
+
+handler:
+    cld
+    phx
+    tsx
+    pha
+    inx
+    inx
+    lda $100,X
+    and #$10
+    bne break
+    phy
+    jsr callirq
+    ply
+    pla
+    plx
+    rti
+
+break:
+    lda #$FF
+    sta RIA_A
+    jmp _exit
diff --git a/libsrc/rp6502/lrand.c b/libsrc/rp6502/lrand.c
new file mode 100644
index 000000000..9a23390e5
--- /dev/null
+++ b/libsrc/rp6502/lrand.c
@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+
+long __fastcall__ lrand(void)
+{
+    return ria_call_long(RIA_OP_LRAND);
+}
diff --git a/libsrc/rp6502/lseek.c b/libsrc/rp6502/lseek.c
new file mode 100644
index 000000000..afa590e63
--- /dev/null
+++ b/libsrc/rp6502/lseek.c
@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+#include <unistd.h>
+
+off_t __fastcall__ lseek(int fd, off_t offset, int whence)
+{
+    /* Modified argument order for short stacking offset */
+    ria_push_long(offset);
+    ria_push_char(whence);
+    ria_set_ax(fd);
+    return ria_call_long_errno(RIA_OP_LSEEK);
+}
diff --git a/libsrc/rp6502/mainargs.s b/libsrc/rp6502/mainargs.s
new file mode 100644
index 000000000..886e39e02
--- /dev/null
+++ b/libsrc/rp6502/mainargs.s
@@ -0,0 +1,16 @@
+; Copyright (c) 2023 Rumbledethumps
+;
+; SPDX-License-Identifier: Zlib
+; SPDX-License-Identifier: BSD-3-Clause
+; SPDX-License-Identifier: Unlicense
+
+.constructor initmainargs, 24
+.import __argc, __argv
+
+.segment "ONCE"
+
+.proc initmainargs
+
+    rts
+
+.endproc
diff --git a/libsrc/rp6502/open.c b/libsrc/rp6502/open.c
new file mode 100644
index 000000000..962614045
--- /dev/null
+++ b/libsrc/rp6502/open.c
@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+#include <errno.h>
+#include <string.h>
+
+int __cdecl__ open(const char *name, int flags, ...)
+{
+    size_t namelen = strlen(name);
+    if (namelen > 255)
+    {
+        return _mappederrno(EINVAL);
+    }
+    while (namelen)
+    {
+        ria_push_char(name[--namelen]);
+    }
+    ria_set_ax(flags);
+    return ria_call_int_errno(RIA_OP_OPEN);
+}
diff --git a/libsrc/rp6502/oserrlist.s b/libsrc/rp6502/oserrlist.s
new file mode 100644
index 000000000..ef322e293
--- /dev/null
+++ b/libsrc/rp6502/oserrlist.s
@@ -0,0 +1,86 @@
+;
+; 2002-07-18, Ullrich von Bassewitz
+; 2022, ChaN
+; 2023, Rumbledethumps
+;
+; Defines the platform-specific error list.
+;
+; The table is built as a list of entries:
+;
+;       .byte   entrylen
+;       .byte   errorcode
+;       .asciiz errormsg
+;
+; and, terminated by an entry with length zero that is returned if the
+; error code could not be found.
+;
+
+.export __sys_oserrlist
+
+.include "rp6502.inc"
+.include "errno.inc"
+
+;----------------------------------------------------------------------------
+; Macros used to generate the list (may get moved to an include file?)
+
+; Regular entry
+.macro sys_oserr_entry code, msg
+    .local Start, End
+Start:
+    .byte End - Start
+    .byte code
+    .asciiz msg
+End:
+.endmacro
+
+; Sentinel entry
+.macro sys_oserr_sentinel msg
+    .byte 0  ; Length is always zero
+    .byte 0  ; Code is unused
+    .asciiz msg
+.endmacro
+
+;----------------------------------------------------------------------------
+; The error message table
+
+.rodata
+__sys_oserrlist:
+
+    sys_oserr_entry ENOENT                 , "No such file or directory"
+    sys_oserr_entry ENOMEM                 , "Out of memory"
+    sys_oserr_entry EACCES                 , "Permission denied"
+    sys_oserr_entry ENODEV                 , "No such device"
+    sys_oserr_entry EMFILE                 , "Too many open files"
+    sys_oserr_entry EBUSY                  , "Device or resource busy"
+    sys_oserr_entry EINVAL                 , "Invalid argument"
+    sys_oserr_entry ENOSPC                 , "No space left on device"
+    sys_oserr_entry EEXIST                 , "File exists"
+    sys_oserr_entry EAGAIN                 , "Try again"
+    sys_oserr_entry EIO                    , "I/O error"
+    sys_oserr_entry EINTR                  , "Interrupted system call"
+    sys_oserr_entry ENOSYS                 , "Function not implemented"
+    sys_oserr_entry ESPIPE                 , "Illegal seek"
+    sys_oserr_entry ERANGE                 , "Range error"
+    sys_oserr_entry EBADF                  , "Bad file number"
+    sys_oserr_entry ENOEXEC                , "Exec format error"
+    sys_oserr_entry EUNKNOWN               , "Unknown OS specific error"
+    sys_oserr_entry FR_DISK_ERR            , "A hard error occurred in the low level disk I/O layer"
+    sys_oserr_entry FR_INT_ERR             , "Assertion failed"
+    sys_oserr_entry FR_NOT_READY           , "The physical drive cannot work"
+    sys_oserr_entry FR_NO_FILE             , "Could not find the file"
+    sys_oserr_entry FR_NO_PATH             , "Could not find the path"
+    sys_oserr_entry FR_INVALID_NAME        , "The path name format is invalid"
+    sys_oserr_entry FR_DENIED              , "Access denied due to prohibited access or directory full"
+    sys_oserr_entry FR_EXIST               , "Access denied due to prohibited access"
+    sys_oserr_entry FR_INVALID_OBJECT      , "The file/directory object is invalid"
+    sys_oserr_entry FR_WRITE_PROTECTED     , "The physical drive is write protected"
+    sys_oserr_entry FR_INVALID_DRIVE       , "The logical drive number is invalid"
+    sys_oserr_entry FR_NOT_ENABLED         , "The volume has no work area"
+    sys_oserr_entry FR_NO_FILESYSTEM       , "There is no valid FAT volume"
+    sys_oserr_entry FR_MKFS_ABORTED        , "The f_mkfs() aborted due to any problem"
+    sys_oserr_entry FR_TIMEOUT             , "Could not get a grant to access the volume within defined period"
+    sys_oserr_entry FR_LOCKED              , "The operation is rejected according to the file sharing policy"
+    sys_oserr_entry FR_NOT_ENOUGH_CORE     , "LFN working buffer could not be allocated"
+    sys_oserr_entry FR_TOO_MANY_OPEN_FILES , "Number of open files > FF_FS_LOCK"
+    sys_oserr_entry FR_INVALID_PARAMETER   , "Given parameter is invalid"
+    sys_oserr_sentinel                       "Unknown error"
diff --git a/libsrc/rp6502/oserror.s b/libsrc/rp6502/oserror.s
new file mode 100644
index 000000000..706bcfa65
--- /dev/null
+++ b/libsrc/rp6502/oserror.s
@@ -0,0 +1,66 @@
+;
+; 2000-05-17, Ullrich von Bassewitz
+; 2022, ChaN
+; 2023, Rumbledethumps
+;
+; int __fastcall__ __osmaperrno (unsigned char oserror);
+;
+; RP6502 will respond with a union of CC65 and FatFs errnos.
+; This will map FatFs errors into the CC65 range for portable code.
+
+EFATFS_START := 32
+
+.include "rp6502.inc"
+.include "errno.inc"
+
+.code
+
+___osmaperrno:
+    cmp #EFATFS_START
+    bmi @L2
+
+    ldx #ErrTabSize
+@L1:
+    cmp ErrTab-2,x      ; Search for the error code
+    beq @L3             ; Jump if found
+    dex
+    dex
+    bne @L1             ; Next entry
+
+; Code not found, return EUNKNOWN
+    lda #<EUNKNOWN
+    ldx #>EUNKNOWN
+@L2:
+    rts
+
+; Found the code
+@L3:
+    lda ErrTab-1,x
+    ldx #$00            ; High byte always zero
+    rts
+
+.rodata
+
+ErrTab:
+
+    .byte FR_DISK_ERR            , EIO       ; A hard error occurred in the low level disk I/O layer
+;   .byte FR_INT_ERR             , EUNKNOWN  ; Assertion failed
+    .byte FR_NOT_READY           , EBUSY     ; The physical drive cannot work
+    .byte FR_NO_FILE             , ENOENT    ; Could not find the file
+    .byte FR_NO_PATH             , ENOENT    ; Could not find the path
+    .byte FR_INVALID_NAME        , EINVAL    ; The path name format is invalid
+    .byte FR_DENIED              , EACCES    ; Access denied due to prohibited access or directory full
+    .byte FR_EXIST               , EEXIST    ; Access denied due to prohibited access
+    .byte FR_INVALID_OBJECT      , EINVAL    ; The file/directory object is invalid
+    .byte FR_WRITE_PROTECTED     , EACCES    ; The physical drive is write protected
+    .byte FR_INVALID_DRIVE       , ENODEV    ; The logical drive number is invalid
+;   .byte FR_NOT_ENABLED         , EUNKNOWN  ; The volume has no work area
+;   .byte FR_NO_FILESYSTEM       , EUNKNOWN  ; There is no valid FAT volume
+;   .byte FR_MKFS_ABORTED        , EUNKNOWN  ; The f_mkfs() aborted due to any problem
+;   .byte FR_TIMEOUT             , EUNKNOWN  ; Could not get a grant to access the volume within defined period
+    .byte FR_LOCKED              , EBUSY     ; The operation is rejected according to the file sharing policy
+    .byte FR_NOT_ENOUGH_CORE     , ENOMEM    ; LFN working buffer could not be allocated
+    .byte FR_TOO_MANY_OPEN_FILES , EMFILE    ; Number of open files > FF_FS_LOCK
+    .byte FR_INVALID_PARAMETER   , EINVAL    ; Given parameter is invalid
+
+ErrTabSize = (* - ErrTab)
diff --git a/libsrc/rp6502/phi2.c b/libsrc/rp6502/phi2.c
new file mode 100644
index 000000000..095580c97
--- /dev/null
+++ b/libsrc/rp6502/phi2.c
@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+
+int __fastcall__ phi2(void)
+{
+    return ria_call_int(RIA_OP_PHI2);
+}
diff --git a/libsrc/rp6502/randomize.c b/libsrc/rp6502/randomize.c
new file mode 100644
index 000000000..a2050c4aa
--- /dev/null
+++ b/libsrc/rp6502/randomize.c
@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+#include <stdlib.h>
+
+// Non-standard cc65
+void _randomize(void)
+{
+    srand(ria_call_int(RIA_OP_LRAND));
+}
diff --git a/libsrc/rp6502/read.c b/libsrc/rp6502/read.c
new file mode 100644
index 000000000..d0b389c4a
--- /dev/null
+++ b/libsrc/rp6502/read.c
@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+#include <unistd.h>
+
+int __fastcall__ read(int fildes, void *buf, unsigned count)
+{
+    int total = 0;
+    while (count)
+    {
+        unsigned blockcount = (count > 256) ? 256 : count;
+        int bytes_read = read_xstack(&((char *)buf)[total], blockcount, fildes);
+        if (bytes_read < 0)
+        {
+            return bytes_read;
+        }
+        total += bytes_read;
+        count -= bytes_read;
+        if (bytes_read < blockcount)
+        {
+            break;
+        }
+    }
+    return total;
+}
diff --git a/libsrc/rp6502/read_xram.c b/libsrc/rp6502/read_xram.c
new file mode 100644
index 000000000..565744e11
--- /dev/null
+++ b/libsrc/rp6502/read_xram.c
@@ -0,0 +1,17 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+
+int __fastcall__ read_xram(unsigned buf, unsigned count, int fildes)
+{
+    ria_push_int(buf);
+    ria_push_int(count);
+    ria_set_ax(fildes);
+    return ria_call_int_errno(RIA_OP_READ_XRAM);
+}
diff --git a/libsrc/rp6502/read_xstack.c b/libsrc/rp6502/read_xstack.c
new file mode 100644
index 000000000..c3b6d098e
--- /dev/null
+++ b/libsrc/rp6502/read_xstack.c
@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+
+int __fastcall__ read_xstack(void *buf, unsigned count, int fildes)
+{
+    int i, ax;
+    ria_push_int(count);
+    ria_set_ax(fildes);
+    ax = ria_call_int_errno(RIA_OP_READ_XSTACK);
+    for (i = 0; i < ax; i++)
+    {
+        ((char *)buf)[i] = ria_pop_char();
+    }
+    return ax;
+}
diff --git a/libsrc/rp6502/ria.s b/libsrc/rp6502/ria.s
new file mode 100644
index 000000000..f040fca61
--- /dev/null
+++ b/libsrc/rp6502/ria.s
@@ -0,0 +1,90 @@
+; Copyright (c) 2023 Rumbledethumps
+;
+; SPDX-License-Identifier: Zlib
+; SPDX-License-Identifier: BSD-3-Clause
+; SPDX-License-Identifier: Unlicense
+
+.include "rp6502.inc"
+
+.export _ria_push_long, _ria_push_int
+.export _ria_pop_long, _ria_pop_int
+.export _ria_set_axsreg, _ria_set_ax
+.export _ria_call_int, _ria_call_long
+.export _ria_call_int_errno, _ria_call_long_errno
+
+.importzp sp, sreg
+.import ___mappederrno, incsp1
+
+.code
+
+; void __fastcall__ ria_push_long(unsigned long val);
+_ria_push_long:
+    ldy sreg+1
+    sty RIA_XSTACK
+    ldy sreg
+    sty RIA_XSTACK
+; void __fastcall__ ria_push_int(unsigned int val);
+_ria_push_int:
+    stx RIA_XSTACK
+    sta RIA_XSTACK
+    rts
+
+; long __fastcall__ ria_pop_long(void);
+_ria_pop_long:
+    jsr _ria_pop_int
+    ldy RIA_XSTACK
+    sty sreg
+    ldy RIA_XSTACK
+    sty sreg+1
+    rts
+
+; int __fastcall__ ria_pop_int(void);
+_ria_pop_int:
+    lda RIA_XSTACK
+    ldx RIA_XSTACK
+    rts
+
+; void __fastcall__ ria_set_axsreg(unsigned long axsreg);
+_ria_set_axsreg:
+    ldy sreg
+    sty RIA_SREG
+    ldy sreg+1
+    sty RIA_SREG+1
+; void __fastcall__ ria_set_ax(unsigned int ax);
+_ria_set_ax:
+    stx RIA_X
+    sta RIA_A
+    rts
+
+; int __fastcall__ ria_call_int(unsigned char op);
+_ria_call_int:
+    sta RIA_OP
+    jmp RIA_SPIN
+
+; long __fastcall__ ria_call_long(unsigned char op);
+_ria_call_long:
+    sta RIA_OP
+    jsr RIA_SPIN
+    ldy RIA_SREG
+    sty sreg
+    ldy RIA_SREG+1
+    sty sreg+1
+    rts
+
+; int __fastcall__ ria_call_int_errno(unsigned char op);
+_ria_call_int_errno:
+    sta RIA_OP
+    jsr RIA_SPIN
+    ldx RIA_X
+    bmi ERROR
+    rts
+
+; long __fastcall__ ria_call_long_errno(unsigned char op);
+_ria_call_long_errno:
+    jsr _ria_call_long
+    bmi ERROR
+    rts
+
+ERROR:
+    lda RIA_ERRNO
+    jmp ___mappederrno
diff --git a/libsrc/rp6502/settime.c b/libsrc/rp6502/settime.c
new file mode 100644
index 000000000..69d4dafe5
--- /dev/null
+++ b/libsrc/rp6502/settime.c
@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+#include <time.h>
+
+int clock_settime(clockid_t clock_id, const struct timespec *tp)
+{
+    ria_set_ax(clock_id);
+    ria_push_long(tp->tv_nsec);
+    ria_push_long(tp->tv_sec);
+    return ria_call_int_errno(RIA_OP_CLOCK_SETTIME);
+}
diff --git a/libsrc/rp6502/stdin_opt.c b/libsrc/rp6502/stdin_opt.c
new file mode 100644
index 000000000..f01d1036c
--- /dev/null
+++ b/libsrc/rp6502/stdin_opt.c
@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+
+int __fastcall__ stdin_opt(unsigned long ctrl_bits, unsigned char str_length)
+{
+    ria_push_long(ctrl_bits);
+    ria_set_a(str_length);
+    return ria_call_int_errno(RIA_OP_STDIN_OPT);
+}
diff --git a/libsrc/rp6502/sysremove.c b/libsrc/rp6502/sysremove.c
new file mode 100644
index 000000000..6b143d672
--- /dev/null
+++ b/libsrc/rp6502/sysremove.c
@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+#include <errno.h>
+#include <string.h>
+
+unsigned char __fastcall__ _sysremove(const char *name)
+{
+    size_t namelen;
+    namelen = strlen(name);
+    if (namelen > 255)
+    {
+        return _mappederrno(EINVAL);
+    }
+    while (namelen)
+    {
+        ria_push_char(name[--namelen]);
+    }
+    return ria_call_int_errno(RIA_OP_UNLINK);
+}
diff --git a/libsrc/rp6502/sysrename.c b/libsrc/rp6502/sysrename.c
new file mode 100644
index 000000000..6d42752ae
--- /dev/null
+++ b/libsrc/rp6502/sysrename.c
@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+#include <errno.h>
+#include <string.h>
+
+unsigned char __fastcall__ _sysrename(const char *oldpath, const char *newpath)
+{
+    size_t oldpathlen, newpathlen;
+    oldpathlen = strlen(oldpath);
+    newpathlen = strlen(newpath);
+    if (oldpathlen + newpathlen > 254)
+    {
+        return _mappederrno(EINVAL);
+    }
+    while (oldpathlen)
+    {
+        ria_push_char(oldpath[--oldpathlen]);
+    }
+    ria_push_char(0);
+    while (newpathlen)
+    {
+        ria_push_char(newpath[--newpathlen]);
+    }
+    return ria_call_int_errno(RIA_OP_RENAME);
+}
diff --git a/libsrc/rp6502/write.c b/libsrc/rp6502/write.c
new file mode 100644
index 000000000..f14c91e59
--- /dev/null
+++ b/libsrc/rp6502/write.c
@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+#include <unistd.h>
+
+int __fastcall__ write(int fildes, const void *buf, unsigned count)
+{
+    int ax, total = 0;
+    while (count)
+    {
+        int blockcount = (count > 256) ? 256 : count;
+        ax = write_xstack(&((char *)buf)[total], blockcount, fildes);
+        if (ax < 0)
+        {
+            return ax;
+        }
+        total += ax;
+        count -= ax;
+        if (ax < blockcount)
+        {
+            break;
+        }
+    }
+    return total;
+}
diff --git a/libsrc/rp6502/write_xram.c b/libsrc/rp6502/write_xram.c
new file mode 100644
index 000000000..379e5a667
--- /dev/null
+++ b/libsrc/rp6502/write_xram.c
@@ -0,0 +1,17 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+
+int __fastcall__ write_xram(unsigned buf, unsigned count, int fildes)
+{
+    ria_push_int(buf);
+    ria_push_int(count);
+    ria_set_ax(fildes);
+    return ria_call_int_errno(RIA_OP_WRITE_XRAM);
+}
diff --git a/libsrc/rp6502/write_xstack.c b/libsrc/rp6502/write_xstack.c
new file mode 100644
index 000000000..4507193ea
--- /dev/null
+++ b/libsrc/rp6502/write_xstack.c
@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) 2023 Rumbledethumps
+ *
+ * SPDX-License-Identifier: Zlib
+ * SPDX-License-Identifier: BSD-3-Clause
+ * SPDX-License-Identifier: Unlicense
+ */
+
+#include <rp6502.h>
+
+int __fastcall__ write_xstack(const void *buf, unsigned count, int fildes)
+{
+    unsigned i;
+    for (i = count; i;)
+    {
+        ria_push_char(((char *)buf)[--i]);
+    }
+    ria_set_ax(fildes);
+    return ria_call_int_errno(RIA_OP_WRITE_XSTACK);
+}
diff --git a/libsrc/rp6502/xreg.s b/libsrc/rp6502/xreg.s
new file mode 100644
index 000000000..81cba6733
--- /dev/null
+++ b/libsrc/rp6502/xreg.s
@@ -0,0 +1,40 @@
+; Copyright (c) 2023 Rumbledethumps
+;
+; SPDX-License-Identifier: Zlib
+; SPDX-License-Identifier: BSD-3-Clause
+; SPDX-License-Identifier: Unlicense
+
+; CC65 will promote variadic char arguments to int. It will not demote longs.
+; int __cdecl__ xreg(char device, char channel, unsigned char address, ...);
+
+.export _xreg
+.importzp sp
+.import addysp, _ria_call_int_errno
+
+.include "rp6502.inc"
+
+.code
+
+.proc _xreg
+
+    ; save variadic size in X
+    tya
+    tax
+
+@copy: ; copy stack
+    dey
+    lda (sp),y
+    sta RIA_XSTACK
+    tya
+    bne @copy
+
+    ; recover variadic size and move sp
+    txa
+    tay
+    jsr addysp
+
+    ; run RIA operation
+    lda #RIA_OP_XREG
+    jmp _ria_call_int_errno
+
+.endproc
diff --git a/src/ca65/main.c b/src/ca65/main.c
index fedbb0d4b..3ec6c84ee 100644
--- a/src/ca65/main.c
+++ b/src/ca65/main.c
@@ -346,6 +346,10 @@ static void SetSys (const char* Sys)
             NewSymbol ("__KIM1__", 1);
             break;
 
+        case TGT_RP6502:
+            NewSymbol ("__RP6502__", 1);
+            break;
+
         default:
             AbEnd ("Invalid target name: '%s'", Sys);
 
diff --git a/src/cc65/main.c b/src/cc65/main.c
index f800ac43e..bef646cdd 100644
--- a/src/cc65/main.c
+++ b/src/cc65/main.c
@@ -303,6 +303,10 @@ static void SetSys (const char* Sys)
             DefineNumericMacro ("__KIM1__", 1);
             break;
 
+        case TGT_RP6502:
+            DefineNumericMacro ("__RP6502__", 1);
+            break;
+
         default:
             AbEnd ("Unknown target system '%s'", Sys);
     }
diff --git a/src/common/target.c b/src/common/target.c
index ad62990bd..b50478e16 100644
--- a/src/common/target.c
+++ b/src/common/target.c
@@ -173,6 +173,7 @@ static const TargetEntry TargetMap[] = {
     {   "pce",          TGT_PCENGINE     },
     {   "pet",          TGT_PET          },
     {   "plus4",        TGT_PLUS4        },
+    {   "rp6502",       TGT_RP6502       },
     {   "sim6502",      TGT_SIM6502      },
     {   "sim65c02",     TGT_SIM65C02     },
     {   "supervision",  TGT_SUPERVISION  },
@@ -221,6 +222,7 @@ static const TargetProperties PropertyTable[TGT_COUNT] = {
     { "cx16",           CPU_65C02,      BINFMT_BINARY,      CTPET   },
     { "sym1",           CPU_6502,       BINFMT_BINARY,      CTNone  },
     { "kim1",           CPU_6502,       BINFMT_BINARY,      CTNone  },
+    { "rp6502",         CPU_65C02,      BINFMT_BINARY,      CTNone  },
 };
 
 /* Target system */
diff --git a/src/common/target.h b/src/common/target.h
index 0cec74b6e..730b8211e 100644
--- a/src/common/target.h
+++ b/src/common/target.h
@@ -88,6 +88,7 @@ typedef enum {
     TGT_CX16,
     TGT_SYM1,
     TGT_KIM1,
+    TGT_RP6502,
     TGT_COUNT                   /* Number of target systems */
 } target_t;