Add pc file for peripheral card ROM

include/apple2.h

@@ -128,6 +128,30 @@ enum memory_mode {
      */
     MEMORY_PAGE2 = 0x8,
     MEMORY_HIRES = 0x10,
+
+    /*
+     * When this is high, expansion ROM is considered in use. That means
+     * that the $C800..$CFFF range will be mapped to the expansion ROM
+     * area of the rom segment (which is at the end), vs. the internal
+     * ROM area, which is at the $0800..$0FFF range within the rom
+     * segment.
+     */
+    MEMORY_EXPROM = 0x20,
+
+    /*
+     * When SLOTCXROM is high, the entire range of $C100..$C7FF will be
+     * mapped to the peripheral ROM area of the rom segment (which is in
+     * the $4100..$47FF address range there); otherwise, $C100...$C7FF
+     * is mapped to internal ROM, located at $0100..$07FF within the
+     * same rom segment.
+     *
+     * It's not possible to map a single peripheral ROM page, with the
+     * exception of slot 3 (via SLOTC3ROM). That page is special because
+     * of its use by the 80-column text card. You can have SLOTC3ROM
+     * high but SLOTCXROM low.
+     */
+    MEMORY_SLOTCXROM = 0x40,
+    MEMORY_SLOTC3ROM = 0x80,
 };
 
 enum bank_switch {

include/apple2.pc.h

@@ -0,0 +1,14 @@
+#ifndef _APPLE2_PC_H_
+#define _APPLE2_PC_H_
+
+#include "apple2.h"
+#include "vm_segment.h"
+
+extern SEGMENT_READER(apple2_pc_read);
+extern SEGMENT_READER(apple2_pc_switch_read);
+extern SEGMENT_WRITER(apple2_pc_switch_write);
+extern SEGMENT_WRITER(apple2_pc_write);
+extern size_t apple2_pc_rom_addr(size_t, vm_8bit);
+extern void apple2_pc_map(vm_segment *);
+
+#endif

sources.cmake

@@ -5,6 +5,7 @@ set(erc_sources
 	apple2.dd.c
 	apple2.draw.c
 	apple2.mem.c
+	apple2.pc.c
 	log.c
 	mos6502.c
 	mos6502.addr.c

src/apple2.mem.c

@@ -4,6 +4,7 @@
 
 #include "apple2.bank.h"
 #include "apple2.dbuf.h"
+#include "apple2.pc.h"
 #include "apple2.h"
 #include "apple2.mem.h"
 #include "objstore.h"
@@ -25,6 +26,8 @@ apple2_mem_map(apple2 *mach, vm_segment *segment)
     // Here we handle the 80STORE bit for our display buffers.
     apple2_dbuf_map(segment);
 
+    apple2_pc_map(segment);
+
     // We will do the mapping for the zero page and stack addresses.
     // Accessing those addresses can be affected by bank-switching, but
     // those addresses do not actually exist in the capital

src/apple2.pc.c

@@ -7,8 +7,19 @@
  * (apple2.dd.c).
  */
 
-#include "apple2.h"
-#include "vm_segment.h"
+#include "apple2.pc.h"
+
+static size_t switch_reads[] = {
+    0xC015,
+    0xC017,
+};
+
+static size_t switch_writes[] = {
+    0xC006,
+    0xC007,
+    0xC00A,
+    0xC00B,
+};
 
 /*
  * Map all of the peripheral ROM space (and peripheral expansion ROM
@@ -17,24 +28,163 @@
  * $C800..$CFFF.
  */
 void
-apple2_pc_map(apple2 *mach, vm_segment *seg)
+apple2_pc_map(vm_segment *seg)
 {
     size_t addr;
+    int i;
+    int rlen, wlen;
 
     for (addr = 0xC100; addr < 0xD000; addr++) {
         vm_segment_read_map(seg, addr, apple2_pc_read);
         vm_segment_write_map(seg, addr, apple2_pc_write);
     }
+
+    rlen = sizeof(switch_reads) / sizeof(size_t);
+    wlen = sizeof(switch_writes) / sizeof(size_t);
+
+    for (i = 0; i < rlen; i++) {
+        vm_segment_read_map(seg, switch_reads[i], apple2_pc_switch_read);
     }
 
+    for (i = 0; i < wlen; i++) {
+        vm_segment_write_map(seg, switch_writes[i], apple2_pc_switch_write);
+    }
+}
+
+/*
+ * This mapper handles the entire potential peripheral ROM space; we
+ * either need to return an address from the beginning of memory, or
+ * near the end.
+ */
 SEGMENT_READER(apple2_pc_read)
 {
     apple2 *mach = (apple2 *)_mach;
 
-    if (mach->memory_mode & MEMORY_EXPROM) {
+    // The address in the rom segment gets translated through a number
+    // of factors
+    addr = apple2_pc_rom_addr(addr, mach->memory_mode);
+
+    // No matter what we do, the segment we return from will always be
+    // the rom segment. This part is non-negotiable.
+    return mach->rom->memory[addr];
 }
 
-    if (mach->memory_mode & MEMORY_SLOTCXROM) {
-        segment = mach->rom;
+/*
+ * Since all of our address spaces are mapped to ROM, we can't write
+ * anything!
+ */
+SEGMENT_WRITER(apple2_pc_write)
+{
+    return;
+}
+    
+
+/*
+ * Given an address from program code, return the corresponding address
+ * in our rom segment. The machine's memory mode is also given as a
+ * factor.
+ */
+size_t
+apple2_pc_rom_addr(size_t addr, vm_8bit mode)
+{
+    size_t rom_addr;
+
+    // This mapper should only be called from the $C000..$CFFF range;
+    // in the rom segment, this group of pages is addressed at
+    // $0000..$0FFF. We can assume that regardless of what addr is, a
+    // subtraction of $C000 would result in a valid address.
+    rom_addr = addr - 0xC000;
+
+    // However, if the EXPROM bit is high, then we want to use expansion
+    // ROM which is located at the _end_ of the rom segment; specifically
+    // in the $4800..$4FFF range.
+    if (rom_addr >= 0x0800 && rom_addr < 0x1000 &&
+        mode & MEMORY_EXPROM
+       ) {
+        rom_addr += 0x4000;
+    }
+
+    // If SLOTCXROM is high, then we want any byte addressed in this
+    // space to reference peripheral ROM (which is again located at the
+    // end of the segment, in exactly the same way that expansion ROM is
+    // placed).
+    if (rom_addr >= 0x0100 && rom_addr < 0x0800 && 
+        mode & MEMORY_SLOTCXROM
+       ) {
+        rom_addr += 0x4000;
+    }
+
+    // One final thing to account for is if the SLOTC3ROM bit is high.
+    // If it is, and if the address has not already been incremented
+    // because SLOTCXROM was _also_ high, then we need to increment just
+    // for this specific page of memory.
+    if (rom_addr >= 0x0300 && rom_addr < 0x0400 &&
+        mode & MEMORY_SLOTC3ROM
+       ) {
+        rom_addr += 0x4000;
+    }
+
+    return rom_addr;
+}
+
+/*
+ * Handle reads to the slot / peripheral ROM switches. I'm not
+ * _entirely_ sure what Apple expects to be returned here, since they
+ * don't indicate as clearly as they did with bank-switch modes; there,
+ * they said you need to return a byte with the 7 bit high, which you
+ * can then use a BPL or a BMI to branch with. Here, they don't specify
+ * bit 7, but I'm going to go with that until I see otherwise.
+ */
+SEGMENT_READER(apple2_pc_switch_read)
+{
+    apple2 *mach = (apple2 *)_mach;
+
+    switch (addr) {
+        case 0xC015:
+            return (mach->memory_mode & MEMORY_SLOTCXROM)
+                ? 0x80
+                : 0x00;
+        case 0xC017:
+            return (mach->memory_mode & MEMORY_SLOTC3ROM)
+                ? 0x80
+                : 0x00;
+    }
+
+    // We shouldn't get here for any practical reason, but...
+    return 0;
+}
+
+/*
+ * Handle writes to the slot switches. There are separate writes to turn
+ * these switches on and off, for each switch, respectively. The value
+ * being written doesn't matter (indeed--you won't see us reference the
+ * value parameter).
+ */
+SEGMENT_WRITER(apple2_pc_switch_write)
+{
+    apple2 *mach = (apple2 *)_mach;
+
+    // We don't care what the value is; if a write happens to any of the
+    // following addresses, we must change the peripheral memory
+    // behavior accordingly.
+    switch (addr) {
+        case 0xC00B:
+            apple2_set_memory_mode(mach,
+                                   mach->memory_mode | MEMORY_SLOTC3ROM);
+            break;
+        case 0xC00A:
+            apple2_set_memory_mode(mach,
+                                   mach->memory_mode & ~MEMORY_SLOTC3ROM);
+            break;
+
+        case 0xC006:
+            apple2_set_memory_mode(mach,
+                                   mach->memory_mode | MEMORY_SLOTCXROM);
+            break;
+
+        case 0xC007:
+            apple2_set_memory_mode(mach,
+                                   mach->memory_mode & ~MEMORY_SLOTCXROM);
+            break;
     }
 }

tests/apple2.pc.c

@@ -0,0 +1,58 @@
+#include <criterion/criterion.h>
+
+#include "apple2.h"
+#include "apple2.pc.h"
+
+static apple2 *mach = NULL;
+
+static void
+setup()
+{
+    mach = apple2_create(100, 100);
+    vm_segment_set_map_machine(mach);
+}
+
+static void
+teardown()
+{
+    apple2_free(mach);
+    vm_segment_set_map_machine(NULL);
+}
+
+TestSuite(apple2_pc, .init = setup, .fini = teardown);
+
+Test(apple2_pc, map)
+{
+    size_t addr;
+    int i;
+    vm_segment *segments[2];
+
+    segments[0] = mach->main;
+    segments[1] = mach->aux;
+
+    for (i = 0; i < 2; i++) {
+        for (addr = 0xC100; addr < 0xD000; addr++) {
+            cr_assert_eq(segments[i]->read_table[addr], apple2_pc_read);
+            cr_assert_eq(segments[i]->write_table[addr], apple2_pc_write);
+        }
+
+        cr_assert_eq(segments[i]->read_table[0xC015], apple2_pc_switch_read);
+        cr_assert_eq(segments[i]->read_table[0xC017], apple2_pc_switch_read);
+        cr_assert_eq(segments[i]->write_table[0xC00B], apple2_pc_switch_write);
+        cr_assert_eq(segments[i]->write_table[0xC00A], apple2_pc_switch_write);
+        cr_assert_eq(segments[i]->write_table[0xC006], apple2_pc_switch_write);
+        cr_assert_eq(segments[i]->write_table[0xC007], apple2_pc_switch_write);
+    }
+}
+
+Test(apple2_pc, rom_addr)
+{
+    cr_assert_eq(apple2_pc_rom_addr(0xC832, MEMORY_DEFAULT), 0x832);
+    cr_assert_eq(apple2_pc_rom_addr(0xC832, MEMORY_SLOTCXROM), 0x832);
+    cr_assert_eq(apple2_pc_rom_addr(0xC832, MEMORY_SLOTC3ROM), 0x832);
+    cr_assert_eq(apple2_pc_rom_addr(0xC232, MEMORY_EXPROM), 0x0232);
+    
+    cr_assert_eq(apple2_pc_rom_addr(0xC832, MEMORY_EXPROM), 0x4832);
+    cr_assert_eq(apple2_pc_rom_addr(0xC732, MEMORY_SLOTCXROM), 0x4732);
+    cr_assert_eq(apple2_pc_rom_addr(0xC332, MEMORY_SLOTC3ROM), 0x4332);
+}