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Refined the comments in the target start-up files.

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Fixed typo errors.  Made the comments consistent across all those files.
This commit is contained in:
Greg King
2014-08-23 14:05:36 -04:00
parent 6df42052b0
commit c7969a78b0
15 changed files with 340 additions and 339 deletions
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135
libsrc/cbm610/crt0.s
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@@ -17,14 +17,14 @@
; ------------------------------------------------------------------------
; BASIC header and a small BASIC program. Since it is not possible to start
; The BASIC header and a small BASIC program. Since it isn't possible to start
; programs in other banks using SYS, the BASIC program will write a small
; machine code program into memory at $100 and start that machine code
; machine code program into memory at $100; and, start that machine code
; program. The machine code program will then start the machine language
; code in bank 1, which will initialize the system by copying stuff from
; the system bank, and start the application.
;
; Here's the basic program that's in the following lines:
; Here's the BASIC program that's in the following lines:
;
; 10 for i=0 to 4
; 20 read j
@@ -39,9 +39,9 @@
; lda #$01
; sta $00 <-- Switch to bank 1 after this command
;
; Initialization is not only complex because of the jumping from one bank
; into another. but also because we want to save memory, and because of
; this, we will use the system memory ($00-$3FF) for initialization stuff
; Initialization is complex not only because of the jumping from one bank
; into another. but also because we want to save memory; and because of
; that, we will use the system memory ($00-$3FF) for initialization stuff
; that is overwritten later.
;
@@ -54,13 +54,15 @@
.byte $30,$2c,$31,$36,$39,$2c,$31,$2c,$31,$33,$33,$2c,$30,$00,$00,$00
;------------------------------------------------------------------------------
; A table that contains values that must be transfered from the system zero
; page into out zero page. Contains pairs of bytes, first one is the address
; in the system ZP, second one is our ZP address. The table goes into page 2,
; but is declared here, because it is needed earlier.
; A table that contains values that must be transferred from the system zero-
; page into our zero-page. Contains pairs of bytes, first one is the address
; in the system ZP, second one is our ZP address. The table goes into page 2;
; but, is declared here because it is needed earlier.
.SEGMENT "PAGE2"
; (We use .proc because we need both a label and a scope.)
.proc transfer_table
.byte $9F, DEVNUM
@@ -76,7 +78,7 @@
; Page 3 data. This page contains the break vector and the bankswitch
; subroutine that is copied into high memory on startup. The space occupied by
; this routine will later be used for a copy of the bank 15 stack. It must be
; saved, since we're going to destroy it when calling bank 15.
; saved since we're going to destroy it when calling bank 15.
.segment "PAGE3"
@@ -84,13 +86,13 @@ BRKVec: .addr _exit ; BRK indirect vector
.proc callbank15
excrts := $FF05 ; In bank 15 rom
excrts := $FF05 ; In bank 15 ROM
.org $FECB
entry: php
pha
lda #$0F ; Bank 15
lda #$0F ; Bank 15
sta IndReg
txa
pha
@@ -113,7 +115,7 @@ entry: php
tya
sec
sbc #7
sta $1FF ; Save new sp
sta $1FF ; Save new sp
tay
tsx
@@ -141,7 +143,7 @@ entry: php
iny
sta (sysp1),y
ldy $1FF ; Restore sp in bank 15
ldy $1FF ; Restore sp in bank 15
lda #.hibyte(expull-1)
sta (sysp1),y
@@ -168,7 +170,7 @@ expull: pla
rts
.if (expull <> $FF2E)
.error "Symbol expull must be aligned with kernal in bank 15"
.error "Symbol expull must be aligned with Kernal in bank 15"
.endif
.reloc
@@ -178,15 +180,15 @@ expull: pla
;------------------------------------------------------------------------------
; The code in the target bank when switching back will be put at the bottom
; of the stack. We will jump here to switch segments. The range $F2..$FF is
; not used by any kernal routine.
; not used by any Kernal routine.
.segment "STARTUP"
Back: sta ExecReg
; We are at $100 now. The following snippet is a copy of the code that is poked
; in the system bank memory by the basic header program, it's only for
; documentation and not actually used here:
; in the system bank memory by the BASIC header program; it's only for
; documentation, and not actually used here:
sei
lda #$01
@@ -194,7 +196,7 @@ Back: sta ExecReg
; This is the actual starting point of our code after switching banks for
; startup. Beware: The following code will get overwritten as soon as we
; use the stack (since it's in page 1)! We jump to another location, since
; use the stack (since it's in page 1)! We jump to another location since
; we need some space for subroutines that aren't used later.
jmp Origin
@@ -206,11 +208,11 @@ Back: sta ExecReg
rts
nop
.word nmi ; NMI vector
.word 0 ; Reset - not used
.word 0 ; Reset -- not used
.word irq ; IRQ vector
.endproc
; Initializers for the extended zeropage. See extzp.s
; Initializers for the extended zero-page. See "extzp.s".
.proc extzp
.word $0100 ; sysp1
@@ -228,12 +230,12 @@ Back: sta ExecReg
.word $eb49 ; ktab4
.endproc
; Switch the indirect segment to the system bank
; Switch the indirect segment to the system bank.
Origin: lda #$0F
sta IndReg
; Initialize the extended zeropage
; Initialize the extended zero-page.
ldx #.sizeof(extzp)-1
L1: lda extzp,x
@@ -241,16 +243,16 @@ L1: lda extzp,x
dex
bpl L1
; Save the old stack pointer from the system bank and setup our hw sp
; Save the old stack pointer from the system bank; and, set up our hw sp.
tsx
txa
ldy #$FF
sta (sysp1),y ; Save system stack point into $F:$1FF
ldx #$FE ; Leave $1FF untouched for cross bank calls
ldx #$FE ; Leave $1FF untouched for cross-bank calls
txs ; Set up our own stack
; Copy stuff from the system zeropage to ours
; Copy stuff from the system zero-page to ours.
lda #.sizeof(transfer_table)
sta ktmp
@@ -264,7 +266,7 @@ L2: ldx ktmp
dec ktmp
bne L2
; Set the interrupt, NMI and other vectors
; Set the interrupt, NMI, and other vectors.
ldx #.sizeof(vectors)-1
L3: lda vectors,x
@@ -272,14 +274,14 @@ L3: lda vectors,x
dex
bpl L3
; Setup the C stack
; Set up the C stack.
lda #.lobyte(callbank15::entry)
sta sp
lda #.hibyte(callbank15::entry)
sta sp+1
; Setup the subroutine and jump vector table that redirects kernal calls to
; Set up the subroutine and jump vector table that redirects Kernal calls to
; the system bank.
ldy #.sizeof(callbank15)
@@ -288,10 +290,10 @@ L3: lda vectors,x
dey
bne @L1
; Setup the jump vector table. Y is zero on entry.
; Set up the jump vector table. Y is zero on entry.
ldx #45-1 ; Number of vectors
@L2: lda #$20 ; JSR opcode
ldx #45-1 ; Number of vectors
@L2: lda #$20 ; JSR opcode
sta $FF6F,y
iny
lda #.lobyte(callbank15::entry)
@@ -303,13 +305,13 @@ L3: lda vectors,x
dex
bpl @L2
; Set the indirect segment to bank we're executing in
; Set the indirect segment to the bank that we're executing in.
lda ExecReg
sta IndReg
; Zero the BSS segment. We will do that here instead calling the routine
; in the common library, since we have the memory anyway, and this way,
; Zero the BSS segment. We will do that here instead of calling the routine
; in the common library, since we have the memory anyway; and this way,
; it's reused later.
lda #<__BSS_RUN__
@@ -319,18 +321,18 @@ L3: lda vectors,x
lda #0
tay
; Clear full pages
; Clear full pages.
ldx #>__BSS_SIZE__
beq Z2
Z1: sta (ptr1),y
iny
bne Z1
inc ptr1+1 ; Next page
inc ptr1+1 ; Next page
dex
bne Z1
; Clear the remaining page
; Clear the remaining page.
Z2: ldx #<__BSS_SIZE__
beq Z4
@@ -341,12 +343,12 @@ Z3: sta (ptr1),y
Z4: jmp Init
; ------------------------------------------------------------------------
; We are at $200 now. We may now start calling subroutines safely, since
; We are at $200 now. We may now start calling subroutines safely since
; the code we execute is no longer in the stack page.
.segment "PAGE2"
; Activate chained interrupt handlers, then enable interrupts.
; Activate the chained interrupt handlers; then, enable interrupts.
Init: lda #.lobyte(__INTERRUPTOR_COUNT__*2)
sta irqcount
@@ -356,11 +358,11 @@ Init: lda #.lobyte(__INTERRUPTOR_COUNT__*2)
jsr initlib
; Push arguments and call main()
; Push the command-line arguments; and, call main().
jsr callmain
; Call module destructors. This is also the _exit entry and the default entry
; Call the module destructors. This is also the exit() entry and the default entry
; point for the break vector.
_exit: pha ; Save the return code
@@ -368,12 +370,12 @@ _exit: pha ; Save the return code
lda #$00
sta irqcount ; Disable custom irq handlers
; Address the system bank
; Address the system bank.
lda #$0F
sta IndReg
; Copy stuff back from our zeropage to the systems
; Copy stuff back from our zero-page to the system's.
.if 0
lda #.sizeof(transfer_table)
@@ -389,13 +391,13 @@ _exit: pha ; Save the return code
bne @L0
.endif
; Place the program return code into ST
; Place the program return code into BASIC's status variable.
pla
ldy #$9C ; ST
sta (sysp0),y
; Setup the welcome code at the stack bottom in the system bank.
; Set up the welcome code at the stack bottom in the system bank.
ldy #$FF
lda (sysp1),y ; Load system bank sp
@@ -416,14 +418,14 @@ _exit: pha ; Save the return code
; easier chaining, we do handle the IRQs in the execution bank (instead of
; passing them to the system bank).
; This is the mapping of the active irq register of the 6525 (tpi1):
; This is the mapping of the active IRQ register of the 6525 (tpi1):
;
; Bit 7 6 5 4 3 2 1 0
; | | | | ^ 50 Hz
; | | | | ^ 50 Hz.
; | | | ^ SRQ IEEE 488
; | | ^ cia
; | | ^ CIA
; | ^ IRQB ext. Port
; ^ acia
; ^ ACIA
irq: pha
txa
@@ -433,41 +435,41 @@ irq: pha
lda IndReg
pha
lda ExecReg
sta IndReg ; Be sure to address our segment
sta IndReg ; Be sure to address our segment
tsx
lda $105,x ; Get the flags from the stack
and #$10 ; Test break flag
lda $105,x ; Get the flags from the stack
and #$10 ; Test break flag
bne dobrk
; It's an IRQ
; It's an IRQ.
cld
; Call chained IRQ handlers
; Call the chained IRQ handlers.
ldy irqcount
beq irqskip
jsr callirq_y ; Call the functions
jsr callirq_y ; Call the functions
; Done with chained IRQ handlers, check the TPI for IRQs and handle them
; Done with the chained IRQ handlers; check the TPI for IRQs, and handle them.
irqskip:lda #$0F
sta IndReg
ldy #TPI::AIR
lda (tpi1),y ; Interrupt Register 6525
lda (tpi1),y ; Interrupt Register 6525
beq noirq
; 50/60Hz interrupt
; 50/60Hz. interrupt
cmp #%00000001 ; ticker irq?
cmp #%00000001 ; ticker IRQ?
bne irqend
jsr scnkey ; Poll the keyboard
jsr UDTIM ; Bump the time
jsr scnkey ; Poll the keyboard
jsr UDTIM ; Bump the time
; Done
; Done.
irqend: ldy #TPI::AIR
sta (tpi1),y ; Clear interrupt
sta (tpi1),y ; Clear interrupt
noirq: pla
sta IndReg
@@ -481,8 +483,7 @@ nmi: rti
dobrk: jmp (BRKVec)
; -------------------------------------------------------------------------
; Data area.
; Data area
.bss
irqcount: .byte 0