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driver.s
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driver.s
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;-----------------------------------------------------------------------------------
; Spectrum Analyzer Display for C64 and PET
;-----------------------------------------------------------------------------------
; (c) Plummer's Software Ltd, 02/11/2022 Initial commit
; David Plummer
; Rutger van Bergen
;-----------------------------------------------------------------------------------
; Serial driver for the C64 using Userport.
;
; Johan Van den Brande, (c) 2014
;
; Based on George Hug's 'Towards 2400' article in the Transactor Magazine Vol 9 #3.
; (https://archive.org/details/transactor-magazines-v9-i03)
;
; Modified by Rutger van Bergen for use with the Spectrum Analyzer Display for C64
;-----------------------------------------------------------------------------------
;-----------------------------------------------------------------------------------
; Constants
;-----------------------------------------------------------------------------------
RS232_DEV = 2
;-----------------------------------------------------------------------------------
; Zeropage addresses not defined by C64.inc
;-----------------------------------------------------------------------------------
XSAV = $97
DFLTN = $99
DFLTO = $9a
PTR1 = $9e
PTR2 = $9f
BITCI = $a8
RIDATA = $aa
BITTS = $b4
NXTBIT = $b5
RODATA = $b6
RIBUF = $f7
ROBUF = $f9
;-----------------------------------------------------------------------------------
; I/O space addresses
;-----------------------------------------------------------------------------------
BAUDOF = $0299
RIDBE = $029b
RIDBS = $029c
RODBS = $029d
RODBE = $029e
ENABL = $02a1
;-----------------------------------------------------------------------------------
; Routine vectors
;-----------------------------------------------------------------------------------
NMISR = $0318
CKISR = $031e
BSOSR = $0326
;-----------------------------------------------------------------------------------
; Kernal ROM addresses
;-----------------------------------------------------------------------------------
RSTKEY = $fe56
RETURN = $febc
OLDOUT = $f1ca
OLDCHK = $f21b
FINDFN = $f30f
SETDEV = $f31f
NOFILE = $f701
RDBYTE = $f14e
EXITRD = $f1b4
;-----------------------------------------------------------------------------------
; Read-only words used by code/kernal API routines
;-----------------------------------------------------------------------------------
strtbit:
strt48: .word 225 ; 225 Made up by Dave after reading Wikipedia
strt24: .word $01cb ; 459 From the Transactor article
strt12: .word $0442 ; 1090
strt03: .word $1333 ; 4915
fullbit:
full48: .word 208 ; 208 Made up by Dave after reading Wikipedia
full24: .word $01a5 ; 421 From the Transactor article
full12: .word $034d ; 845 not referenced directly, but through Y
full03: .word $0d52 ; 3410 register indexing
; Control Registers
;
; 300 - $06 3284 0xCD4
; 1200 - $08 822 0x336
; 2400 - $0A 410 0x19a
; 4800 - We lack the technology to predict the next element in this pattern
baudrate = 10 ; chr$(10) == $0A == 2400 baud
databits = 0
stopbit = 0
wire = 0
duplex = 0
parity = 0
serial_config:
.byte baudrate + databits + stopbit
.byte wire + duplex + parity
;-----------------------------------------------------------------------------------
; OpenSerial: Setup the code to handle RS232 I/O
;-----------------------------------------------------------------------------------
OpenSerial:
lda #RS232_DEV
ldx #<serial_config
ldy #>serial_config
jsr SETNAM
lda #RS232_DEV
tax
tay
jsr SETLFS
jsr OPEN
jsr ser_setup
rts
;-----------------------------------------------------------------------------------
; GetSerialChar: Will fetch a character from the receive buffer and store it into A.
; If no data is available, SER_ERR_NO_DATA is returned in X/Y.
;-----------------------------------------------------------------------------------
GetSerialChar:
ldx #RS232_DEV
jsr CHKIN
jsr ser_rshavedata
beq @nodata
jsr GetBufferChar
pha
jsr CLRCH
pla
ldx #<SER_ERR_OK
ldy #>SER_ERR_OK
rts
@nodata:
jsr CLRCH
lda #$ff
ldx #<SER_ERR_NO_DATA
ldy #>SER_ERR_NO_DATA
rts
;-----------------------------------------------------------------------------------
; GetBufferChar: This is a minimised call to get the character from the buffer.
; The Kernal code does not allow zero bytes (0x00)... this does.
;-----------------------------------------------------------------------------------
GetBufferChar:
jsr RDBYTE
bcc @exit
jmp EXITRD
@exit:
clc
rts
;-----------------------------------------------------------------------------------
; PutSerialChar: Output character in A.
;-----------------------------------------------------------------------------------
PutSerialChar:
pha
ldx #RS232_DEV
jsr CHKOUT
pla
jsr BSOUT
jsr CLRCH
rts
;-----------------------------------------------------------------------------------
; StartSerial: Start serial communication. OpenSerial must have been called already.
;-----------------------------------------------------------------------------------
StartSerial = ser_enable
;-----------------------------------------------------------------------------------
; CloseSerial: Teardown serial comms. We just disable it.
;-----------------------------------------------------------------------------------
CloseSerial = ser_disable
;-----------------------------------------------------------------------------------
; GetKeyboardChar: Get a character from the keyboard. In this case, just use GETIN
;-----------------------------------------------------------------------------------
GetKeyboardChar = GETIN
;-----------------------------------------------------------------------------------
ser_setup:
; set things up for our baud rate
; lda strt48
; sta ser_strtlo
; lda strt48+1
; sta ser_strthi
; lda full48
; sta ser_fulllo
; lda full48+1
; sta ser_fullhi
lda #<ser_nmi64
ldy #>ser_nmi64
sta NMISR
sty NMISR+1
lda #<ser_nchkin
ldy #>ser_nchkin
sta CKISR
sty CKISR+1
lda #<ser_nbsout
ldy #>ser_nbsout
sta BSOSR
sty BSOSR+1
rts
;-----------------------------------------------------------------------------------
ser_nmi64:
pha ; new nmi handler
txa
pha
tya
pha
cld
ldx CIA2_TB+1 ; sample timer b hi byte
lda #$7f ; disable cia nmi's
sta CIA2_ICR
lda CIA2_ICR ; read/clear flags
bpl @notcia ; (restore key)
cpx CIA2_TB+1 ; tb timeout since timer b sampled?
ldy CIA2_PRB ; (sample pin c)
bcs @mask ; no
ora #$02 ; yes, set flag in acc.
ora CIA2_ICR ; read/clear flags again
@mask:
and ENABL ; mask out non-enabled
tax ; these must be serviced
lsr ; timer a? (bit 0)
bcc @ckflag ; no
lda CIA2_PRA ; yes, put bit on pin m
and #$fb
ora NXTBIT
sta CIA2_PRA
@ckflag:
txa
and #$10 ; *flag nmi (bit 4)
beq @nmion ; no
lda ser_strtlo ; yes, start-bit to tb ; STARTBIT
sta CIA2_TB
lda ser_strthi
sta CIA2_TB+1
lda #$11 ; start tb counting
sta CIA2_CRB
lda #$12 ; *flag nmi off, tb on
eor ENABL ; update mask
sta ENABL
sta CIA2_ICR ; enable new config
lda ser_fulllo ; change reload latch
sta CIA2_TB ; to full-bit time
lda ser_fullhi
sta CIA2_TB+1
lda #$08 ; # of bits to receive
sta BITCI
bne @chktxd ; branch always
@notcia:
ldy #$00
jmp RSTKEY
@nmion:
lda ENABL ; re-enable nmi's
sta CIA2_ICR
txa
and #$02 ; timer b? (bit 1)
beq @chktxd ; no
tya ; yes, get sample of pin c
lsr
ror RIDATA ; rs232 is lsb first
dec BITCI ; byte finished?
bne @txd ; no
ldy RIDBE ; yes, byte to buffer
lda RIDATA
sta (RIBUF),y ; (no overrun test)
inc RIDBE
lda #$00 ; stop timer b
sta CIA2_CRB
lda #$12 ; tb nmi off, *flag on
@switch:
ldy #$7f ; disable nmi's
sty CIA2_ICR ; twice
sty CIA2_ICR
eor ENABL ; update mask
sta ENABL
sta CIA2_ICR ; enable new config
@txd:
txa
lsr ; timer a?
@chktxd:
bcc @exit ; no
dec BITTS ; yes, byte finished?
bmi @char ; yes
lda #$04 ; no, prep next bit
ror RODATA ; (fill with stop bits)
bcs @store
@low:
lda #$00
@store:
sta NXTBIT
@exit:
jmp RETURN ; restore regs, rti
@char:
ldy RODBS
cpy RODBE ; buffer empty?
beq @txoff ; yes
;getbuf
lda (ROBUF),y ; no, prep next byte
inc RODBS
sta RODATA
lda #$09 ; # bits to send
sta BITTS
bne @low ; always - do start bit
@txoff:
ldx #$00 ; stop timer a
stx CIA2_CRA
lda #$01 ; disable ta nmi
bne @switch ; always
;--------------------------------------
ser_disable:
pha ; turns off modem port
@test:
lda ENABL
and #$03 ; any current activity?
bne @test ; yes, test again
lda #$10 ; no, disable *flag nmi
sta CIA2_ICR
lda #$02
and ENABL ; currently receiving?
bne @test ; yes, start over
sta ENABL ; all off, update mask
pla
rts
;--------------------------------------
ser_nbsout:
pha ; new bsout
lda DFLTO
cmp #RS232_DEV
bne ser_notmod
pla
;rsout:
sta PTR1 ; output to modem
sty XSAV
ser_point:
ldy RODBE
sta (ROBUF),y ; not official till pointer bumped
iny
cpy RODBS ; buffer full?
beq ser_fulbuf ; yes
sty RODBE ; no, bump pointer
ser_strtup:
lda ENABL
and #$01 ; transmitting now?
bne ser_ret3 ; yes
sta NXTBIT ; no, prep start bit,
lda #$09
sta BITTS ; # bits to send,
ldy RODBS
lda (ROBUF),y
sta RODATA ; and next byte
inc RODBS
lda ser_fulllo ; full tx bit time
sta CIA2_TA
lda ser_fullhi
sta CIA2_TA+1
lda #$11 ; start timer a
sta CIA2_CRA
lda #$81 ; enable ta nmi
ser_change:
sta CIA2_ICR ; nmi clears flag if set
php ; save irq status
sei ; disable irq's
ldy #$7f ; disable nmi's
sty CIA2_ICR ; twice
sty CIA2_ICR
ora ENABL ; update mask
sta ENABL
sta CIA2_ICR ; enable new config
plp ; restore irq status
ser_ret3:
clc
ldy XSAV
lda PTR1
rts
ser_fulbuf:
jsr ser_strtup
jmp ser_point
ser_notmod:
pla ; back to old bsout
jmp OLDOUT
;--------------------------------------
ser_nchkin:
jsr FINDFN ; new chkin
bne ser_nosuch
jsr SETDEV
lda DEVNUM
cmp #RS232_DEV
bne ser_back
sta DFLTN
ser_enable:
sta PTR1 ; enable rs232 input
sty XSAV
;baud:
; BAUD BAUDOF+1 (BAUDOF+1) & #6
; 2400 == $960 9 9 & 6
; 1200 == $4B0 4 4 & 6
; 300 == $12C 1 1 & 6
; BUGBUG if easy and possible let this work as it used to, even though
; I have NFI what it's supposed to be doing. Let bigger heads prevail.
;
; lda BAUDOF+1 ; set receive to same
; and #$06 ; baud rate as xmit
; tay
; lda strt24,y
ldy #BAUD2400 ; We could allow selection by Y reg here if desired
lda strtbit,y ;
sta ser_strtlo ; overwrite values used by nmi handler
lda strtbit+1,y
sta ser_strthi
lda fullbit,y
sta ser_fulllo
lda fullbit+1,y
sta ser_fullhi
lda ENABL
and #$12 ; *flag or tb on?
bne ser_ret1 ; yes
sta CIA2_CRB ; no, stop tb
lda #$90 ; turn on flag nmi
jmp ser_change
ser_nosuch:
jmp NOFILE
ser_back:
lda DEVNUM
jmp OLDCHK
;--------------------------------------
; rsget:
sta PTR1 ; input from modem
sty PTR2
ldy RIDBS
cpy RIDBE ; buffer empty?
beq ser_ret2 ; yes
lda (RIBUF),y ; no, fetch character
sta PTR1
inc RIDBS
ser_ret1:
clc ; cc = char in acc.
ser_ret2:
ldy PTR2
lda PTR1
;last:
rts ; cs = buffer was empty
;----------------------------------------
; A = 0 when no data
; A = 1 when data
ser_rshavedata:
lda #0
ldy RIDBS
cpy RIDBE ; buffer empty?
beq @rsempty ; no
lda #1
@rsempty:
rts