IBM XT 5160 Technical Reference page 275

SOURCE (BIOS FOR THE IBM PERSONAL COMPUTER XT) 1 1 /08/82
;-----INT 14------------------------------------------------------------
RS232 10
-TH I S ROUT I NE PROV I DES BYTE STREAM I/O TO THE COMMUN I CAT IONS
PORT ACCORD I NG TO THE PARAMETERS:
( AH) = 0 I NIT I AL I ZE THE COMMUN I CA T IONS PORT
(AU HAS PARAMETERS FOR INITIALIZATION
(OX) = PARAMETER INDICATING WHICH RS232 CARD (0,1 ALLOWED)
DATA AREA RS232 BASE CONTA I NS THE BASE ADDRESS OF THE 8250 ON THE
CARD LOCATION 400H CONTAINS UP TO 4 RS232 ADDRESSES POSSIBLE
DATA AREA LABEL RS232 TIM OUT (BYTE) CONTAINS OUTER LOOP COUNT
VALUE FOR TIMEOUT (DEFAULT=I)
OUTPUT
AX MOD I F I ED ACCORD I NG TO PARMS OF CALL
ALL OTHERS UNCHANGED
VECTOR TO APPROPR I ATE ROUT I NE
STI
'I NTERRUPTS BACK ON
PUSH
OS SAVE SEGMENT
PUSH OX
PUSH SI
PUSH 01
PUSH CX
PUSH BX
MOV
SI,DX
RS232 VALUE TO S I
MOV DI,DX
SHL SI, I
WORD OFFSET
CALL DDS
MOV DX,RS232_BASE[SI]
GET BASE ADDRESS
OR DX,DX
TEST FOR 0 BASE ADDRESS
JZ
A3 RETURN
OR AH,AH
TEST FOR (AH) =0
JZ A4
COMMUN INIT
DEC AH
TEST FOR (AH) = I
JZ A5
SEND AL
DEC AH
TEST FOR (AH) =2
JZ
A 12
RECE I VE INTO AL
A2:
DEC AH
TEST FOR (AH) =3
JNZ A3
JMP A 18
COMMUN I CA TI ON STATUS
A3:
RETURN FROM RS232
POP BX
POP
CX
POP 01
POP S I
POP OX
POP OS
IRET
RETURN TO CALLER, NO ACTION
ON RETURN, CONDITIONS SET AS IN CALL TO COMMO STATUS (AH=3)
( AH) = I SEND THE CHARACTER IN (AL ) OVER THE COMMO LINE
(AL) REG I STER I S PRESERVED
ON EX IT, BIT 7 OF AH I S SET I F THE ROUT I NE WAS UNABLE
TO TRANSMIT THE BYTE OF DATA OVER THE LINE.
IF BI T 7 OF AH I S NOT SET, THE REMA I NDER OF AH
IS SET AS IN A STATUS REQUEST, REFLECTING THE
CURRENT STATUS OF THE LINE.
(AH) =2 RECE I VE A CHARACTER IN (AL) FROM COMMO LINE BEFORE
RETURN I NG TO CALLER
ON EXIT, AH HAS THE CURRENT LINE STATUS, AS SET BY THE
THE STATUS ROUT I NE, EXCEPT THAT THE ONLY BI TS
LEFT ON ARE THE ERROR BI TS (7,4,3,2,
I )
IF AH HAS BIT 7 ON (TIME .OUT) THE REMAINING
BI TS ARE NOT PRED I CT ABLE.
THUS, AH I S NON ZERO ONLY WHEN AN ERROR
OCCURRED.
(AH) =3 RETURN THE COMMO PORT STATUS IN (AX)
AH CONTAINS THE LINE STATUS
BIT 7 = T I ME OUT
BI T 6 = TRANS SH I FT REG I STER EMPTY
BI T 5 = TRAN HOLD I NG REG I STER EMPTY
BI T 4 = BREAK DETECT
BI T 3 = FRAM I NG ERROR
BIT 2 = PARITY ERROR
BIT 1 = OVERRUN ERROR
BIT 0 = DATA READY
AL CONT A I NS THE MODEM ST ATUS
BI T 7 = RECE I VED LI NE SIGNAL DETECT
BIT 6 = RING INDICATOR
BI T 5 = DATA SET READY
BIT 4 = CLEAR TO SEND
BIT 3 = DELTA RECE I VE LI NE SIGNAL DETECT
BI T 2 = TRA I LI NG EDGE RING DETECTOR
BIT I = DELTA DATA SET READY
BI T 0 = DELTA CLEAR TO SEND
1 0
--WORD LENGTH--
10 - 7 BITS
11 - 8 BITS
2
STOPBIT
o -
1
1 - 2
4 3
-PAR ITY--
XO - NONE
01 - ODD
11 - EVEN
7 6 5
----- BAUD RATE --
000 - 1 10
001 - 150
010 - 300
011 - 600
100 - 1200
101 - 2400
110 - 4800
111 - 9600
ASSUME
CS:CODE,DS:DATA
ORG OE729H
A
I LABEL WORD TABLE OF INIT VALUES
OW 1047 110 BAUD
OW 768 150
OW 384
300
OW 192
600
OW 96
1200
OW 48
2400
OW 24 4800
OW
12 9600
RS232
-
10 PROC
FAR
146
i
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
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1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
LINE
LOC OBJECT
E739
E739 FB
E73A IE
E73B 52
E73C 56
E73D 57
E73E 51
E73F 53
E740 8BF2
E742 88FA
E744 D1E6
E746 E81013
E7 49 8B14
E74B OBD2
E74D 7413
E74F OAE4
E751 7416
E753 FECC
E755 7445
E757 FECC
E759 746A
E75B
E75B FECC
E75D 7503
E75F E98300
E762
E762 5B
E763 59
E764 5F
E765 5E
E766 5A
E767 IF
E768 CF
E729
E729
E729 1704
E72B 0003
E72D 8001
E72F COOO
E731 6000
E733 3000
E735 1800
E737 OCOO
5-128 PC-XT System BIOS (11/08/82)