itty-bitty-vtty/modem.s
2021-04-04 20:22:43 -04:00

237 lines
2.1 KiB
ArmAsm

lst off
exp off
*
* read modem port
*
*
cmdb equ $c038
cmda equ $c039
datab equ $c03a
dataa equ $c03b
cout equ $fded
read mac
ldx #]1
if 3=]1
stx cmda
lda cmda
else
stx cmdb
lda cmdb
fin
sta buffer,x
<<<
lst on
org $0800
mx %11
db $01 ; prodos boot id
boot
* clc
* xce
* cli
sei
ldx #24
lda #$80+$0d
:cs jsr cout
dex
bpl :cs
* just in case.
lda cmdb
lda cmdb
init
* reset channel b
ldx #9
lda #%01010001
stx cmdb
sta cmdb
nop
nop
* x16 clock mode, 1 stop bit, no parity
ldx #4
lda #%01000100
stx cmdb
sta cmdb
* 8 bits/char, rx disabled.
ldx #3
lda #%11000000
stx cmdb
sta cmdb
* 8 data bits, RTS
ldx #5
lda #%01100010
stx cmdb
sta cmdb
ldx #11
lda #%01010000
stx cmdb
sta cmdb
* 9600 baud
ldx #12
lda #10
stx cmdb
sta cmdb
* 9600 baud
ldx #13
lda #0
stx cmdb
sta cmdb
* disable baud rate generator
ldx #14
lda #0
stx cmdb
sta cmdb
* enable baud rate generator
ldx #14
lda #%00000001
stx cmdb
sta cmdb
* 8 bits/char, rx enabled.
ldx #3
lda #%11000001
stx cmdb
sta cmdb
* 8 data bits, tx enabled, RTS
ldx #5
lda #%01101010
stx cmdb
sta cmdb
* disable interrupts
ldx #15
lda #0
stx cmdb
sta cmdb
* reset ext/status interrupts
ldx #0
lda #%00010000
stx cmdb
sta cmdb
* disable interrupts
ldx #1
lda #0
stx cmdb
sta cmdb
* reset ch b ptr to 0?
lda cmdb
* status, visible, master interrupts disabled
ldx #9
lda #%00010001
stx cmdb
sta cmdb
nop
nop
* read registers - 0, 1, 2, 3, 8, 10, 12, 13, 15
* 3 is channel A only.
loop
read 0
read 1
read 2
read 3
read 8
read 10
read 12
read 13
read 15
ldx #15
:cmp lda buffer,x
cmp prev,x
bne :delta
dex
bpl :cmp
bra wailoop
:delta
ldx #0
:print
lda buffer,x
phx
pha
lsr
lsr
lsr
lsr
tax
lda hex,x
jsr cout
pla
and #$0f
tax
lda hex,x
jsr cout
lda #" "
jsr cout
plx
inx
cpx #16
bcc :print
lda #$80+$0d
jsr cout
* store prev. values.
ldx #15
:copy lda buffer,x
sta prev,x
dex
bpl :copy
wailoop
* wai
brl loop
nop
nop
stp
hex asc "0123456789abcdef"
buffer ds 16
prev ds 16
lst off
* ds \
ds 1024+$0800-*
sav modem.bin