IBM 5150 - 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