IOtech Digital488, Manual

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3-2, Command Descriptions
7-17-01
Digital488 User’s Manual
Bus Input/Output Gn
The Bus Output command determines whether input port data, output port data or both will be transmitted
on the bus when the Digital488 is addressed to talk. The amount of data sent is dependent
on the Pn command.
The G0 default mode causes all input and output port data to be sent to the controller when addressed
to talk. The G1 mode causes only data from the ports programmed as inputs to be returned when addressed
to talk. The G2 mode causes only data from ports programmed as outputs to be returned when addressed
to talk.
If all ports are programmed as outputs with G1 selected and the Digital488 is addressed to talk,
nothing will be transmitted and the bus will hang. The converse will also cause the bus to hang with all
ports programmed as inputs and
G2 selected.
G0
Input and output port data is send on talk
G1 Only input port data is sent on talk
G2 Only output port data is sent on talk
Example:
CLEAR 718 reset the Digital488
OUTPUT 718;"P0C1X" port1 as output, ports 2-5 as input
OUTPUT 718;"G1X" select only input ports
ENTER 718; A$ read data from the input ports
DISP A$ display shows FFFFFFFF (data is
dependent on what is connected.
OUTPUT 718;"G2X" select output ports
ENTER 718; A$ read data from the output ports
DISP A$ display shows 00 (outputs default to 0)
Configure Cn
Ports 1 thru 5 are configured as inputs or outputs with the Configure command.
Each port is eight bits wide. At power-on, all ports are initialized as inputs. The Configure command is
usually the first command to be sent after power on. All ports programmed as outputs will be set to a logic
zero after receiving the
Configure command. The actual output level is dependent on the Invert command
( I16 ) .
Cn Mode n (0 thru 5) defines which ports are input and output
Port 5 4 3 2 1
C0 in in in in in
C1 in in in in out
C2
in in in out out
C3 in in out out out
C4 in out out out out
C5 out out out out out
in = programmed as an input port
out = programmed as an output port
Example:
CLEAR 718 reset the Digital488
OUTPUT 718;"C1X" select port 1 as output, ports 2 thru 5
as inputs