IOtech Digital488, Manual

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Digital488 User’s Manual
11-20-01
IEEE488 Primer, 4-5
Multiline Commands
Multiline (bus) commands are sent by the Active Controller over the data bus with ATN asserted.
These commands include addressing commands for talk, listen, Untalk and Unlisten.
Go To Local (GTL)
This command allows the selected devices to be manually controlled. ($01)
Listen Address Group (LAG)
There are 31 (0 to 30) listen addresses associated with this group. The 3 most significant bits of the data
bus are set to 001 while the 5 least significant bits are the address of the device being told to listen.
Unlisten (UNL)
This command tells all bus devices to Unlisten. The same as Unaddressed to Listen. ($3F)
Talk Address Group (TAG)
There are 31 (0 to 30) talk addresses associated with this group. The 3 most significant bits of the data bus
are set to 010 while the 5 least significant bits are the address of the device being told to talk.
Untalk (UNT)
This command tells bus devices to Untalk. The same as Unaddressed to Talk. ($5F)
Local Lockout (LLO)
Issuing the LLO command prevents manual control of the instrument's functions. ($11)
Device Clear (DCL)
This command causes all bus devices to be initialized to a pre-defined or power up state. ($14)
Selected Device Clear (SDC)
This causes a single device to be initialized to a pre-defined or power up state. ($04)
Serial Poll Disable (SPD)
The SPD command disables all devices from sending their Serial Poll status byte. ($19)
Serial Poll Enable (SPE)
A device which is Addressed to Talk will output its Serial Poll status byte after SPE is sent and ATN is
unasserted. ($18)
Group Execute Trigger (GET)
This command usually signals a group of devices to begin executing a triggered action. This allows actions
of different devices to begin simultaneously. ($08)
Take Control (TCT)
This command passes bus control responsibilities from the current Controller to another device, which has
the ability to control. ($09)
Secondary Command Group (SCG)
These are any one of the 32 possible commands (0 to 31) in this group. They must immediately follow a
talk or listen address. ($60 to $7F)