Measurement Computing Digital488/80A - Manual (Page 63)

G - Bus Input/Output
SYNTAX Gn Define mode n of data transmission on the IEEE 488 bus when the Digital488/80A
is addressed to Talk, where n = value from 0 to 4 .
G0 (Default) Input and output port data are sent when addressed to Talk.
G1 Only input port data is sent
G2 Only output port data is sent
G3 Buffered input and output data are sent
G4 Continuous buffered input and output data are sent
G? Returns current bus input/output mode n .
Note: The amount of data sent is dependent upon the Port Select ( P ) command.
DESCRIPTION
The Bus Input/Output (
G ) command determines whether input port data, output port data, both input and output port
data, or buffered data are transmitted on the bus when the Digital488/80A is addressed to Talk. The amount of data
sent is dependent upon the Port Select (
P ) command.
The Bus Input/Output (
G ) default mode G0 causes all input and output port data to be sent to the controller when
addressed to Talk. Mode G1 causes only data from the ports programmed as inputs to be returned when addressed to
Talk. Mode G2 causes only data from ports programmed as outputs to be returned when addressed to Talk.
Mode
G3 causes data in the data buffer to be returned when addressed to Talk. Both input and output data (all 40 bits)
are returned in this mode. If the count of readings in the buffer is 0, the Digital488/80A holds off the bus until the next
transition of EDR and another reading has been collected and buffered. After the EDR transition, it returns the newly
collecting reading. The Digital488/80A must be readdressed to Talk to perform subsequent buffered output of EDR
captured data. Mode
G4 is identical to mode G3 except that the Digital488/80A performs subsequent buffered output
of EDR captured data until the controller stops handshaking.
Note: If all ports are programmed as outputs with mode
G1 selected, and the Digital488/80A is addressed to Talk,
nothing is transmitted and the bus hangs. The converse also causes the bus to hang if all ports are
programmed as inputs with mode
G2 selected.
CAUTION
Because the Configuration (C) command is used, the following programming
example(s) will not work properly if the HVCX1 option is installed with a conflicting
hardware configuration. To be safe, remove the HVCX1 board and replace it with the
jumper board to run the example(s).
EXAMPLE
PRINT#1,"CLEAR08" Line 1: Reset the Digital488/80A.
PRINT#1,"OUTPUT08;P0C1R0X" Line 2: Configure Port 1 as output, Ports 2 through 5 as inputs.
PRINT#1,"OUTPUT08;G1X" Line 3: Select only input ports for data.
PRINT#1,"ENTER08",
INPUT#2,A$ Line 5: Read data from the Digital488/80A input ports.
PRINT A$ Line 6: Display shows: FFFFFFFF (Data is dependent upon
what is connected.)
Digital488/80A User’s Manual 967695 Digital488/80A Commands 57