Atari 400 Technical Reference Manual page 313

ERR LINE
ADDR
B1 B2 B3 B4
SIO ( SERIAL BUS INPUT/OUTPUT CONTROLLER )
PAGE 52
2275 EBF1 60 RTS
2276
2277
2278
2279
2280
2281
i ;
2282
i
SEND ENABLE SUBROUTINE
2283
2284 EBF2 A9 07 SENDEN: LDA #$07 iMASK OFF PREVIOUS SERIAL BUS CONTROL BITS
2285 EBF4 2D 32 02 AND SSKCTL
2286 EBF7 09 20 ORA
#$20 iSET TRANSMIT MODE
2287
2288 EBF9 AC 00 03 LDY DDEVIC
2289 EBFC CO 60 CPY #CASET
2290
EBFE
DO OC
BNE NOTCAS iBRANCH IF NOT CASSETTE
2291
2292 ECOO 09 08 ORA #$08 iSET THE FSK OUTPUT BIT
2293
2294 EC02 AO 07
LDY
#LOTONE iSET FSK TONE FREGUENCIES
2295 EC04 8C 02 D2 STY
AUDF2
2296
EC07
AO 05 LDY
#HITONE
2297 EC09 8C 00 D2 STY AUDFl
2298
2299 ECOC 8D 32 02 NOTCAS: STA SSKCTL iSTORE NEW VALUE TO SYSTEM MASK
2300 ECOF
8D OF D2 STA SKCTL
iSTORE TO ACTUAL REGISTER
2301
2302 EC12 A9 C7 LDA
#$C7
iMASK OFF PREVIOUS SERIAL BUS INTERRUPT BITS
2303 EC14 25 10 AND POKMSK
2304 EC16 09 10
ORA
#$10 iENABLE OUTPUT DATA NEEDED INTERRUPT
2305
2306
2307 EC18 4C 31 EC JMP CONTIN
iGO
CONTINUE IN RECEIVE ENABLE SUBROUTINE
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
i
RECEIVE ENABLE SUBROUTINE
2319
2320 EC1B A9 07 RECVEN: LOA #$07 iMASK OFF PREVIOUS SERIAL BUS CONTROL BITS
2321 EC1D 2D 32 02
AND SSKCTL
2322 EC20 09 10 ORA
#$10
iSET RECEIVE MODE ASYNCH.
2323 EC22 8D 32 02 STA SSKCTL iSTORE NEW VALUE TO SYSTEM MASK
2324 EC25 8D OF D2 STA SKCTL iSTORE TO ACTUAL REGISTER
2325
2326 EC28
80 OA D2 STA SKRES iRESET SERIAL PORT/KEYBOARD STATUS REGISTER
2327
2328 EC2B A9 C7 LDA #$C7 iMASK OFF PREVIOUS SERIAL BUS INTERRUPT BITS