Instruction manual

6.4.3 IEEE-488 Operational Sequence Guidelines

Most interface communication tasks require a sequence of coded mes-

sages to be sent over the interface. It is recommended that a careful study of

the available controller capabilities be made many of them assigning one

programming instruction to these sequences. Different controllers will not

necessarily have identical sequences or program instructions.

The following sequences are recommendations only.

DATA TRANSFER

ATN DATA FUNCTION

1 UNL Inhibits all current listeners

1 (LAD) 1Each address sent enables a specific device re

ceives future data bytes

1 (LAD) n More than one address may be sent if multiple listeners

desired.

0 (TAD) The address sent enables a specific device to send data

0 (DAB) Data bytes sent by currently enabled talker to all currently

enabled listeners.

1 UNT Disables the talker on receipt of last character.

UNL = Unlisten

LAD = Listen address of specific device

TAD = Talk address of specific device

DAB = Data bytes

UNT = Untalk

SERIAL POLL

ATN DATA FUNCTION

1 UNL Prevents other devices listening to status sent

1 SPE Puts interface into serial poll mode during which all

devices send status instead of data when addressed.

1 (LAD) n More than one address may be sent if multiple listeners

desired.

0 (TAD)n Enable a specific device to send status.

Within these loop devices should be sequentially enabled.

1 SBN

or SBA Status byte sent by enabled device. If SBN sent, loop

should be repeated. If SBA sent, the enabled device

is identified as having sent SRQ over the Interface

and will automatically remove it.

1 SPD Disables Serial Poll mode

1 UNT Disable Last Talker.