DevHelp VideoPause

This service is called by physical device drivers when the controller reports a DMA overrun. VideoPause starts or stops high-priority threads. This halts threads using the CPU for video transfers, which allows the diskette DMA to complete termination properly.

Syntax

C

USHORT APIENTRY DevHelp_VideoPause( USHORT OnOff );

Assembler

MOV   AL,VideoPause_Flag       ; VideoPause flag.
MOV   DL,DevHlp_VideoPause
                              Off= 0
                              On = 1

CALL  [Device_Help]

Parameters

C

OnOff (USHORT)

Video_Pause_Off 0

Video_Pause_On 1

Assembler

MOV   AL,VideoPause_Flag       ; VideoPause flag.

Return Code

C

Success Indicator: Clear if successful.

Possible errors: Carry flag set if error.

Assembler

   'C' Clear if successful.

   'C' Set if error.

Remarks

VideoPause can be called at task time or interrupt time. This service is used after a retry has failed. To avoid impairing system performance, VideoPause is turned on only long enough to accomplish the transfer. If multiple physical device drivers have turned VideoPause on, it is not turned off until all of them have turned it off.

Example Code

C

#include  "dhcalls.h"

USHORT APIENTRY DevHelp_VideoPause( USHORT OnOff );