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rs232trans2
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.PAGE 'RS-232 TRANSMITT'
; RSTRAB - ENTRY FOR NMI CONTINUE ROUTINE
; RSTBGN - ENTRY FOR START TRANSMITTER
;
; RSR - 8/18/80
;
; VARIABLES USED
; BITTS - # OF BITS TO BE SENT (<>0 NOT DONE)
; NXTBIT - BYTE CONTAINS NEXT BIT TO BE SENT
; ROPRTY - BYTE CONTAINS PARITY BIT CALCULATED
; RODATA - STORES DATA BYTE CURRENTLY BEING TRANSMITTED
; RODBS - OUTPUT BUFFER INDEX START
; RODBE - OUTPUT BUFFER INDEX END
; IF RODBS=RODBE THEN BUFFER EMPTY
; ROBUF - INDIRECT POINTER TO DATA BUFFER
; RSSTAT - RS-232 STATUS BYTE
;
; XXX US - NORMAL BIT PATH
; XXX US - WORST CASE PARITY BIT PATH
; XXX US - STOP BIT PATH
; XXX US - START BIT PATH
;
RSTRAB LDA BITTS ;CHECK FOR PLACE IN BYTE...
BEQ RSTBGN ;...DONE, =0 START NEXT
;
BMI RST050 ;...DOING STOP BITS
;
LSR RODATA ;SHIFT DATA INTO CARRY
LDX #00 ;PREPARE FOR A ZERO
BCC RST005 ;YES...A ZERO
DEX ;NO...MAKE AN $FF
RST005 TXA ;READY TO SEND
;
EOR ROPRTY ;CALC INTO PARITY
STA ROPRTY
;
DEC BITTS ;BIT COUNT DOWN
BEQ RST010 ;WANT A PARITY INSTEAD
;
RSTEXT TXA ;CALC BIT WHOLE TO SEND
AND #$20 ;GOES OUT CB2
STA NXTBIT
RTS
.PAGE 'RS-232 TRANSMITT'
; CALCULATE PARITY
; NXTBIT =0 UPON ENTRY
;
RST010 LDA #$20 ;CHECK 6551 REG BITS
BIT M51CDR
BEQ RSPNO ;...NO PARITY, SEND A STOP
BMI RST040 ;...NOT REAL PARITY
BVS RST030 ;...EVEN PARITY
;
LDA ROPRTY ;CALC ODD PARITY
BNE RSPEXT ;CORRECT GUESS
;
RSWEXT DEX ;WRONG GUESS...ITS A ONE
;
RSPEXT DEC BITTS ;ONE STOP BIT ALWAYS
LDA M51CTR ;CHECK # OF STOP BITS
BPL RSTEXT ;...ONE
DEC BITTS ;...TWO
BNE RSTEXT ;JUMP
;
RSPNO ;LINE TO SEND CANNOT BE PB0
INC BITTS ;COUNTS AS ONE STOP BIT
BNE RSWEXT ;JUMP TO FLIP TO ONE
;
RST030 LDA ROPRTY ;EVEN PARITY
BEQ RSPEXT ;CORRECT GUESS...EXIT
BNE RSWEXT ;WRONG...FLIP AND EXIT
;
RST040 BVS RSPEXT ;WANTED SPACE
BVC RSWEXT ; WANTED MARK
.SKI 3
; STOP BITS
;
RST050 INC BITTS ;STOP BIT COUNT TOWARDS ZERO
LDX #$FF ;SEND STOP BIT
BNE RSTEXT ;JUMP TO EXIT
;
.PAG 'RS-232 TRANSMITT'
; RSTBGN - ENTRY TO START BYTE TRANS
;
RSTBGN LDA M51CDR ;CHECK FOR 3/X LINE
LSR A
BCC RST060 ;3 LINE...NO CHECK
BIT D2ORB ;CHECK FOR...
BPL DSRERR ;...DSR ERROR
BVC CTSERR ;...CTS ERROR
;
; SET UP TO SEND NEXT BYTE
;
RST060 LDA #0
STA ROPRTY ;ZERO PARITY
STA NXTBIT ;SEND START BIT
LDX BITNUM ;GET # OF BITS
RST070 STX BITTS ;BITTS=#OF BITTS+1
;
RST080 LDY RODBS ;CHECK BUFFER POINTERS
CPY RODBE
BEQ RSODNE ;ALL DONE...
;
LDA (ROBUF)Y ;GET DATA...
STA RODATA ;...INTO BYTE BUFFER
INC RODBS
;
; CARRIAGE RETURN DELAY
;
CMP #$13 ;DELAY ON C/R
BNE RST090 ;NONE
LDX M51ADJ ;M51CRD
BEQ RST090
LDY #$40 ;TURN OF T1
STY D1IER
;
RST085 LDY #0 ;DELAY LOOP
JSR TOARTS
JSR TOARTS
DEY
BNE RST085
DEX
BNE RST085
LDX #$C0 ;TURN T1 BACK ON
STX D1IER
;
RST090
TOARTS RTS
.SKI 3
; SET ERRORS
;
DSRERR LDA #$40 ;DSR GONE ERROR
.BYT $2C
CTSERR LDA #$10 ;CTS GONE ERROR
ORA RSSTAT
STA RSSTAT
;
; ERRORS TURN OFF T1
;
RSODNE LDA #$40 ;KILL T1 NMI
STA D1IER
RTS
.SKI 3
; BITCNT - CAL # OF BITS TO BE SENT
; RETURNS #OF BITS+1
;
BITCNT LDX #9 ;CALC WORD LENGTH
LDA #$20
BIT M51CTR
BEQ BIT010
DEX ;BIT 5 HIGH IS A 7 OR 5
BIT010 BVC BIT020
DEX ;BIT 6 HIGH IS A 6 OR 5
DEX
BIT020 RTS
.END
; RSR 8/24/80 CORRECT SOME MISTAKES
; RSR 8/27/80 CHANGE BITNUM BASE TO #BITS+1
; RSR 9/23/80 ADD C/R DELAY