[KERNAL] add legacy/c816 extended APIs (X16Community#280)

Makefile

@@ -41,7 +41,11 @@ KERNAL_CORE_SOURCES = \
 	kernal/cbm/nmi.s \
 	kernal/cbm/irq.s \
 	kernal/cbm/util.s \
-	kernal/cbm/serial.s
+	kernal/cbm/serial.s \
+	kernal/x16/extapi.s \
+	kernal/x16/65c816/interrupt.s \
+	kernal/x16/65c816/stack.s \
+	kernal/x16/65c816/extapi16.s
 
 KERNAL_GRAPH_SOURCES = \
 	kernal/graph/graph.s \
@@ -66,8 +70,6 @@ KERNAL_DRIVER_SOURCES = \
 	kernal/drivers/x16/i2c.s \
 	kernal/drivers/x16/smc.s \
 	kernal/drivers/x16/rtc.s \
-	kernal/drivers/x16/65c816/interrupt.s \
-	kernal/drivers/x16/65c816/stack.s \
 	kernal/drivers/generic/softclock_timer.s
 
 KERNAL_SOURCES = \
@@ -182,6 +184,16 @@ GENERIC_DEPS = \
 
 KERNAL_DEPS = \
 	$(GENERIC_DEPS) \
+	kernal/cbm/channel/channelio.s \
+	kernal/cbm/channel/clall.s \
+	kernal/cbm/channel/close.s \
+	kernal/cbm/channel/errorhandler.s \
+	kernal/cbm/channel/load.s \
+	kernal/cbm/channel/messages.s \
+	kernal/cbm/channel/open.s \
+	kernal/cbm/channel/openchannel.s \
+	kernal/cbm/channel/save.s \
+	kernal/cbm/channel/x16additions.s \
 	$(GIT_SIGNATURE)
 
 KEYMAP_DEPS = \

kernal/cbm/channel/channel.s

@@ -94,6 +94,11 @@ untlk = $ffab
 
 .export savehl
 
+; misc x16 additions
+.export clear_status
+.export get_fa
+
+
 .segment "ZPCHANNEL" : zeropage
 ;                      C64 location
 ;                         VVV
@@ -146,4 +151,5 @@ stah	.res 1           ;$C2
 .include "load.s"
 .include "save.s"
 .include "errorhandler.s"
+.include "x16additions.s"
 

kernal/cbm/channel/x16additions.s

@@ -0,0 +1,8 @@
+
+clear_status:
+    stz status
+    rts
+
+get_fa:
+    lda fa
+    rts

kernal/vectors.s

@@ -31,6 +31,8 @@
 
 .import savehl
 
+.import extapi, extapi16
+
 .import c816_abort_emulated, c816_clall_thunk, c816_getin_thunk
 
 .include "banks.inc"
@@ -39,10 +41,8 @@
 
 ; *** this is space for new X16 KERNAL vectors ***
 ;
-; !!! DO NOT RELY ON THEIR ADDRESSES JUST YET !!!
-;
-	.byte 0,0,0                    ; $FEA8
-	.byte 0,0,0                    ; $FEAB
+	jmp extapi16                   ; $FEA8
+	jmp extapi                     ; $FEAB
 	.byte 0,0,0                    ; $FEAE
 	jmp mciout                     ; $FEB1
 	jmp i2c_batch_read             ; $FEB4

kernal/x16/65c816/extapi16.s

@@ -0,0 +1,42 @@
+.import stack_push, stack_pop
+.import stack_enter_kernal_stack, stack_leave_kernal_stack
+
+.export extapi16
+
+.include "65c816.inc"
+
+.segment "UTIL"
+
+.setcpu "65816"
+
+.A16
+.I16
+
+; This API call expects and requires m=0, x=0, e=0
+extapi16:
+    php ; preserve flags
+    set_carry_if_65c816
+    bcc unsupported
+    phx ; preserve X parameter
+    asl ; translate API call number to jump table entry
+    tax
+    lda apitbl,x
+    plx ; restore old X
+    plp ; restore flags
+    pha ; push api address-1 onto stack
+    rts ; jump to api
+
+unsupported:
+    plp
+secrts:
+    sec
+    rts
+
+apitbl:
+    .word secrts-1 ; slot 0 is reserved
+    .word stack_push-1                 ; API 1
+    .word stack_pop-1                  ; API 2
+    .word stack_enter_kernal_stack-1   ; API 3
+    .word stack_leave_kernal_stack-1   ; API 4
+
+

kernal/x16/extapi.s

@@ -0,0 +1,35 @@
+.import clear_status
+.import get_fa
+
+.export extapi
+
+.segment "UTIL"
+
+; This API call expects and requires e=1
+extapi:
+    pha ; reserve two free spots on the stack
+    pha
+    php ; preserve caller flags
+    phx ; preserve caller X parameter
+    asl
+    tax
+    lda apitbl,x   ; low byte of jump table entry
+    pha
+    lda apitbl+1,x ; high byte of jump table entry
+    tsx
+    sta $105,x     ; store API high byte on stack
+    pla
+    sta $104,x     ; store API low byte on stack
+    plx            ; restore caller X
+    plp            ; restore caller flags
+    rts            ; jump to api
+
+secrts:
+    sec
+    rts
+
+apitbl:
+    .word secrts-1 ; slot 0 is reserved
+    .word clear_status-1      ; API 1
+    .word get_fa-1            ; API 2
+

kernsup/kernsup.inc

@@ -1,5 +1,5 @@
-.byte 0,0,0                       ; $FEA8
-.byte 0,0,0                       ; $FEAB
+bridge extapi16                   ; $FEA8
+bridge extapi                     ; $FEAB
 .byte 0,0,0                       ; $FEAE
 bridge mciout                     ; $FEB1
 bridge i2c_batch_read             ; $FEB4