Measurement-computing Personal488 rev.3.0 For DOS & Windows 3.Xi Uživatelský manuál stáhnout pdf (Strana 118)

II. SOFTWARE GUIDES - 8. Driver488/DRV 8K. Other Languages

Personal488 User’s Manual, Rev. 3.0 II-103

ARM Condition Detection

It is sometimes desirable to be able to easily check for asynchronous bus conditions, such as Service

Request (

SRQ

), without having to use the Driver488/DRV

STATUS

command. This can be

accomplished by using the light pen interrupt emulation feature of Driver488/DRV. When this feature

is enabled, Driver488/DRV preempts the normal function of the light pen BIOS status request interrupt.

Instead of returning the light pen switch status, this interrupt returns an indicator that is non-zero if any

of the

ARM

conditions are true. See the

ARM

command in “Section III: Command References” for more

details about the conditions that can be checked.

There are two items to notice about this routine: it uses the BIOS video interrupt

10h

rather than the

DOS function call interrupt

21h

, and it checks twice to see if a condition has been detected. The test

must be repeated if

IOCTL Read

is used to check the Driver488/DRV status.

IOCTL Read

causes the

light pen interrupt emulation to return

no interrupt

status on the next status read, regardless of the

actual

ARM

condition status. This allows the BASIC function

ON PEN

to operate properly, but requires

the status to be checked twice in other languages.

Sample Program

name DB” IEEE”, 0 ;Driver488/DRV device name

ieee DWO ;Place to hold Driver488/DRV file

handle

ioctlbufDB 0 ;IOCTL Read response buffer

ioctllenEQU $-ioctllen ;Length of buffer

cr EQU 0Dh ;Carriage-return

lf EQU 0Ah ;Line-feed

hello DB “HELLO”,,cr,,lf ;HELLO command with terminators

hellolen EQU $-hello ;HELLO command length

response DB 256 DUP (?) ;Place to put Driver488 response

responselen EQ $-response ;Length of response buffer

;

recvdlen DW ? ;Place to keep # chars in response

start mov Ah, 3Dh ;Open function

mov AL, 02 ;Access code = read/write

mov DX, offset name ;DS:DX-name

int 21h ;Execute DOS function

jc error ;Error if carry set

mov ieee,AX ;Save file handle

mov AH, 3Eh ;Close function

mov BX, ieee ;File handle

int 21h ;Execute DOS function

jc error ;Check for error

mov AX, 4400h ;DOS GetDeviceData Function

mov BX, ieee ;File handle for Driver488/DRV

int 21h ;Execute DOS function

mov DH, 0 ;Must clear

or DL, 20h ;Set “don’t check for control

characters” bit

mov AX, 4401h ;DOS SetDeviceData Function

mov BX, ieee ;File handle

int 21h ;Execute DOS function

Checking the Driver488/DRV light pen emulation status is straight forward, as illustrated by the

following table.

mov AX,0400h ;Test light pen function

int 10h ;BIOS video interrupt

or AH,AH ;Check AH

jnz GotInt ;Non-zero means interrupt

mov AX,0400h ;Repeat the test

int 10h

or AH,AH

jnz GotInt

1 2 ... 113 114 115 116 117 118 119 120 121 122 123 ... 399 400

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