IBM 5150 PC Technical Reference (6025005, August, 1981) (PDF)

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1351 MOV AX,OEOAH ; LINE FEED CHARS
1352: ItH 10H
1353 RET
1354 P _HSG EHOP
1355 ;--- INT 19 ----------------------------­
1356 I BOOT STRAP LOADER
1357 IF A 5 1/4" DISKETTE DRIVE IS AVAIlABLE
1358 ON THE SYSTEM. TRACK 0, SECTOR 1 IS READ INTO THE
1359 BOOT LOCATION (SEG~IENT O. OFFSET 7COO}
1360 Aim CONTROL IS TRANSFERRED THERE.
1361
1362 IF TIiERE IS NO DISKETTE DRIVE. OR IF THERE IS
1363 IS A HAROWARE ERROR CONTROL IS TRANSFERREO
1364 TO THE CASSETTE BASIC E~Y POINT.
1365
1366 I IPl ASSUMPTIONS
1367 8255 PORT bOH El:lT 0
1368 = 1 IF IPL FROH DISKETTE
1369 ; ------------------------------.--------­
1370 ASSUME CS:CDDE.DS:DATA
1371 BOOT.STRAP PROC NEAR
1372
1373 STI 1 ENABLE INTERRUPTS
1374 HOV AX,DATA ; ESTABLISH ADDRESSING
1375 HOV OS,AX
1376 HOV AX. EQUIPJUG ; GET THE EQUIPMENT SWITCKE'
1377 TEST ALd J ISOLATE IPL SENSE SWITCH
1378 JZ H3 ;, GO TO CASSETTE BASIC ENTRY POINT
1379
1380 ;------ MUST LOAD SYSTEM FROM DISKETTE -­ ex HAS RETRY COUHT
1381
1382 NOV CX.4 ; SET RETRY COUNT
1383 HI: J IPL.SYSTEH
1384 PUSH ex ; SAVE RETRY COl.mT
1385 HOV AH,O ; RESET THE DISKETTE SYSTEM
1386 INT 13ft j DISKETTE.IO
1387 JC HZ I IF ERROR. TRY AGAIN
1388 HOV AH,2 ; READ IN THE SINGLE SECTOR
1389 MOV BX.O ; TO THE BOOT LOCATION
1390 MOV ES,BX
1391 HOV eX,oFFSET BOOT.LOCN
139Z HOV OX,O I DRIVE 0, HEAD 0
1393 MOV CX.! ; SECTOR I, TRACK 0
1394 NOV AL,I ; READ ONE SECTOR
n95 INT IlH i DISKETTE.IO
1396 POP ex j RECOVER RETRY COUNT
1397 JNe H4 ; CF SET BY UNSUCCESSFUL READ
1398 LOOP HI j DO IT FOR RETRY TIMES
1399
1400 j------ UNABLE TO IPL FROM THE DISKETTE
1401
1402 H3: I CASSETTE_JUMP:
1403 INT 18H ; USE INTERRUPT VECTOR TO GET TO BASIC
1404
1405 1------ IPL WAS SUCCESSFUL
1406
1407 H4:
1406
1409
1410 ; -----INT 14----­---------------------------­
1411 ;RS232_IO
1412 THIS ROUTINE PROVIDES BYTE STREAM I/O TO THE: COf1MUNICATIOHS
1413 PORT ACCORDING TO THE: PARAMETERS:
1414 (AH )=0 INITIALIZE TItE COMMUNICATIONS PORT
1415 j AL) HAS PARMS fOR INITIALIZATION
1416
1417 7 • 4 I
1416 ----­ BAUD RATE -­ -PARITY-­ STOPBIT --WORD lENGTH-­
1419
1420 000 - 110 xo - NONE o ­ 1 10 - 7 BITS
1421 001 - 150 01 - COD 1 - Z 11 - 8 BITS
1422 010 - 300 11 - EVEN
1423 011 - 600
1424 100 - 1200
1425 101 - 24QO
1426 110 - 4600
1427 III - 9600
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