From 7e65f64c6a5067c9c509da4fcd50413716f5fd88 Mon Sep 17 00:00:00 2001
From: cuz <cuz@b7a2c559-68d2-44c3-8de9-860c34a00d81>
Date: Thu, 25 Oct 2001 19:13:36 +0000
Subject: [PATCH] Debug the rs232 routines. This involved using two new
 segments, STARTUP and NMI to make sure the NMI handler is loaded into the low
 16K of memory which are active when the control is passed from the ROM NMI
 stub to the user handler.

git-svn-id: svn://svn.cc65.org/cc65/trunk@1086 b7a2c559-68d2-44c3-8de9-860c34a00d81
---
 libsrc/c128/c128.inc |  1 +
 libsrc/c128/crt0.s   | 12 +++++++++---
 libsrc/c128/rs232.s  | 30 ++++++++++++++++++++++--------
 3 files changed, 32 insertions(+), 11 deletions(-)

diff --git a/libsrc/c128/c128.inc b/libsrc/c128/c128.inc
index d97abd48c..8e4415e70 100644
--- a/libsrc/c128/c128.inc
+++ b/libsrc/c128/c128.inc
@@ -172,6 +172,7 @@ CIA2_CRB	= $DD0F
 ; I/O: MMU
 
 MMU_CR		= $FF00
+CC65_MMU_CFG	= $0E	; Bank 0 with kernal ROM
 
 ; ---------------------------------------------------------------------------
 ; Super CPU
diff --git a/libsrc/c128/crt0.s b/libsrc/c128/crt0.s
index a1c97ce76..25ec5e6c3 100644
--- a/libsrc/c128/crt0.s
+++ b/libsrc/c128/crt0.s
@@ -18,7 +18,6 @@
 ; ------------------------------------------------------------------------
 ; Constants
 
-CC65_MMU_CFG	= $0E	; Bank 0 with kernal ROM
 IRQInd		= $2FD	; JMP $0000 - used as indirect IRQ vector
 
 ; ------------------------------------------------------------------------
@@ -45,9 +44,16 @@ tmp3:	      	.res	1
 tmp4:	      	.res	1
 regbank:      	.res	6	; 6 byte register bank
 
-zpspace	= * - zpstart		; Zero page space allocated
+zpspace	= * - zpstart	 	; Zero page space allocated
 
-.code
+; Place the startup code in a special segment to cope with the quirks of
+; c128 banking. Do also create an empty segment named "NMI" to avoid
+; warnings if the rs232 routines are not used.
+
+.segment        "NMI"
+; empty
+
+.segment       	"STARTUP"
 
 ; ------------------------------------------------------------------------
 ; BASIC header with a SYS call
diff --git a/libsrc/c128/rs232.s b/libsrc/c128/rs232.s
index 5718cba07..0c5d7cf5c 100644
--- a/libsrc/c128/rs232.s
+++ b/libsrc/c128/rs232.s
@@ -27,6 +27,8 @@
 	.export	       	_rs232_init, _rs232_params, _rs232_done, _rs232_get
 	.export	      	_rs232_put, _rs232_pause, _rs232_unpause, _rs232_status
 
+	.include	"c128.inc"
+
 
 NmiExit = $ff33     ;exit address for nmi
 
@@ -120,7 +122,7 @@ _rs232_init:
 
 ;** check for super-cpu at 20 MHz
 
-      	bit 	$d0bc
+      	bit 	SCPU_Detect
    	bmi 	@L4
    	bit 	$d0b8
    	bvs 	@L4
@@ -142,14 +144,14 @@ _rs232_init:
 
 ;** set up nmi's
 
-   	lda 	$318
-   	ldy 	$319
+   	lda 	NMIVec
+   	ldy 	NMIVec+1
    	sta 	NmiSave+0
    	sty 	NmiSave+1
    	lda 	#<NmiHandler
    	ldy 	#>NmiHandler
-   	sta 	$318
-   	sty 	$319
+   	sta 	NMIVec
+   	sty 	NMIVec+1
 
 ;** set default to 2400-8N1, enable interrupts
 
@@ -313,8 +315,8 @@ _rs232_done:
 
    	lda 	NmiSave+0
       	ldy 	NmiSave+1
-   	sta 	$318
-   	sty 	$319
+   	sta 	NMIVec
+   	sty 	NMIVec+1
 
 ; Flag uninitialized
 
@@ -530,8 +532,17 @@ _rs232_status:
 ; C64  @  57.6k: 177 cycles avail, worstAvail=177-43? = 134
 ; SCPU @ 230.4k: 868 cycles avail: for a joke!
 ;
+; Because of the C128 banking, the NMI handler must go into the non banked
+; memory, since the ROM NMI entry point will switch to a configuration where
+; only the lowest 16K of RAM are visible. We will place the NMI handler into
+; it's own segment and map this segment into the lower 16K in the linker 
+; config.
+  
+.segment 	"NMI"
 
 NmiHandler:
+	lda	#CC65_MMU_CFG		;(2)
+	sta	MMU_CR			;(4)
        	lda    	ACIA+RegStatus       	;(4) ;status ;check for byte received
      	and 	#$08           		;(2)
      	beq 	@L9			;(2*)
@@ -553,7 +564,7 @@ NmiHandler:
 ; Assert flow control
 
 @L2:  	lda 	RtsOff       		;(3)  ;assert flow control if buffer space too low
-    	sta 	ACIA+RegCommand	;(4) ;command
+    	sta 	ACIA+RegCommand		;(4) ;command
     	sta 	Stopped      		;(3)
     	jmp 	NmiExit      		;(3)
 
@@ -569,6 +580,9 @@ NmiHandler:
 @L4:   	jmp 	NmiExit
 
 @L9:	jmp 	NmiContinue
+		     
+
+.code
 
 ;----------------------------------------------------------------------------
 ;