IBM 5150 Technical Reference page 157

LOC OBJ
LINE SOLIRCE
EC44 75E8 2407
JHZ
K.5 I DO ANOTHER CYCLE
EC46 58 2408
pop
AX
I RECOVER CONTROL
EC47 E661
2409
CXJT KB_CTl,A.L I OUTPUT THE CONTROL
EC49 E912FE
2410 JHP
K27
2411 ; ---------------.------------ -----------­
2412 ROS CHECKSUM SUBROUTINE
2413
i ---------------------------------------­
EC4C
2414 ; NEXT.RDS.MODULE
EC4C B90020 2415 HOV CX.8192 I NUt1BER OF BYTES TO ADO
EC4F 2416 RDS.CHECKSUM.CNT: ; ENTRY FOR OPTIONAL RDS TEST
EC4F 32CO
2417 XOR Al,U
EC51 2418
e26:
ECSI 0207 2419
ADD
Al,OS:
lex]
EC53 43
2420 INC BX I POINT TO NEXT BYTE
EC54 EZFB 2421 LOOP
C2'
I ADD All BYTES IN RDS MODULE
EC56 OACO 2422
OR
AL,Al
J SUM
=
O?
ECS8 C3
2423
RET
2424
RDS.CHECKSUM
ENDP
2425
2426
J--
INT 13 -------------------------------------------------------------­
2427 J DISKETTE 110
2428 J THIS INTERFACE PROVIDES ACCESS TO THE 5 1/4" DISKETTE DRIVES
2429 J INPUT
2430 (AH)=O RESET DISKETTE SYSTEM
2431 HARD RESET TO NEC, PREPARE COtl1Atl), RECAl REQUIRED
2432
ON ALL DRIVES
2433 UH )=1 READ THE STATUS OF THE SYSTEH INTO IAll
2434 DISKETTE_STATUS FROH LAST OPERATION IS USED
2435
2436 J REGISTERS FOR READIWRITEIVERIFYlFORMAT
2437 (DU -
D~IVE t-n.JHBE~
(0-3 ALLOWED. VA-WE CHECKED)
2438 CDH) - HEAD NUMBER (0-1 ALLOWED. NOT VAWE CHECKED)
2439 (CH) - TRACK NUHBER (0-39. NOT VALUE CHECKED)
2440 (CL) -
SECTO~
NUl'IBER 11-8. NOT VALUE CHECKED.
2441 NOT USED FOR FORMAlI
2442 (AL) -
Nl.JMBE~
OF SECTOR'S ( MAX = 8. NOT VALUE CHECKED. HOT USED
2443 FOR FORMAT)
2444 (ES:BXI - ADDRESS Of BUffER
I
HOT
REQUI~ED
FOR
VE~IFy)
2445
2446
IAHJ=2 READ THE DESIRED SECTORS INTO MEMORY
2447
(AH )=3 WRITE
THE
DESIRED
SECTO~S F~OM
MEHORY
2448
IAHJ=4 VERIFY THE DESIRED SECTORS
2449
I AH )=5 fORHAT THE DESIRED TRACK
2450
FOR THE fORHAT OPERATION. THE BUFFER POINTER IES.BX)
2451
tlUST POINT TO THE COLLECTION OF DESIRED ADDRESS FIELDS
2452 FOR THE TRACK. EACH FIHD IS COMPOSED Of 4 BYTES.
2453
(C.H.R.N). WHERE C = TRACK NUMBER. H=HEAD HUf1BER.
2454
R = SECTOR NUMBER. N= NUHBER OF BYTES PER SECTOR
2455 (00=128. 01=256. 02=512. 03=1024J. THERE tllST BE ONE
2456
ENTRY FOR EVERY SECTOR ON THE TRACK. THIS INfORMATION
2457 IS USED TO FIND THE REQUESTED SECTOR DlRING READIWRITE
2458
ACCESS.
2459
2460 ; DATA VARIABLE -- DISK_POINTER
2461 DOlSLE 1ol0RD POINTER TO THE CURRENT SET Of DISKETTE PARAHETERS
2462
J OUTPUT
2463 AH
=
STATUS OF OPERATION
2464 STATUS BITS ARE DEFINED IN THE EQUATES fOR
2465 DISKETTE_STATUS VARIABLE 1N THE DATA SEGMENT OF TH1S
2466 MDOULE.
2467 CY
=
0 SUCCESSfUL OPERATION (AH=O ON RETURN)
2468
CY
=
1 FAILED OPERATION IAH HAS ERROR REASONJ
2469
FOR READ/WRITEIVERIFY
2470
DS.BX.DX.CH,CL PRESERVED
2471
Al
=
NUMBER OF SECTORS ACTUAllY READ
2472
*****
AL MAY NOT BE CORRECT IF TIME OUT ERROR OCCURS
2473 NOTE: IF AN ERROR IS REPORTED BY THE DISKETTE CODE. THE
2474 APPROPRIATE ACTION IS TO RESET THE DISKETTE. THEN ~ETRY
2475 THE OPERATION. ON READ ACCESSES.
NO
MOTOR START DELAY
2476 IS TAKEN.
so
THAT THREE RETRIES ARE REQUIRED ON REAOS
2477 TO ENSURE THAT THE PROBLEt1 IS NOT DUE TO HOTOR
2478 START-UP.
2479
J-----------------------------------------------------------------------­
2480 ASSUME CS:COOE,OS:DATA.ES:DATA
EC59 2481
ORG OEC59H
EC59 2482 DISKETTE_IO PROC fAR
EC59 FB 2483 STI
INTERRUPTS BACK ON
5-64 System BIOS