VPASS - Variable-length pass

General

Application area:	Starting, interrupting and terminating; see "Starting, interrupting and terminating"
Macro type:	Type R; see "R-type macros"

Macro description

The VPASS macro is used to relinquish control of the processor for a specified period, i.e. the user task is set to a wait state. The waiting period specification can be made relative to the CPU rate.

Macro format and description of operands

VPASS

number / (1)

,MSEC=N / Y

,CPUDEP=N / Y

number
Number of seconds or milliseconds during which the task is placed in the wait state, specified either as a decimal or a hexadecimal digit (X'....').

(1)
Specifies that register R1 is loaded with the required number of seconds or milliseconds.

Value range

• Specification in seconds:

  • direct entry: 0 <= number <= 4095 (=X'0FFF')

  • Register R1: 0 <= number <= 21599

• Specification in milliseconds: 1 <= number <= 999 (=X'3E7')

MSEC=
Defines the unit of measurement for the “number” specification.

N
Specification in seconds.

Y
Specification in milliseconds (ms).

CPUDEP=

Specifies whether the period of time is to be made relative to the CPU rate.

N
The time specification is not made relative.

Y
The time specification is not changed in the case of 1-MOPS servers (servers working at a rate of one million operations per second).
In the case of faster servers, the specified waiting time is reduced, relative to the CPU rate. With slower servers this time is increased correspondingly.

Making the time relative specification rate is advisable only when specified waiting times are short, since the number of executed instructions cannot otherwise be estimated precisely enough.

Notes on the macro call

• Time specifications <= 500 ms do not lead to deactivation of the task. The task remains in the active waiting state.

• The specification number = 0 sec corresponds to a waiting time of 500 ms (for reasons of compatibility).

For an example see the section “Contingency processes”.