Measurement Computing Digital232 - Manual (Page 34)

Section 3 Command Descriptions
3.12
OUTPUT SELECT Gn
The Output Select command determines the I/O port from which data will be
transmitted when the Digital232 outputs data to its serial port. The amount of data
sent is dependent on the Pn command. In any port mode other than P0, only the 8 bits
selected by the Port command will be output from the Digital232 serial port.
The default mode, G0 causes all 40 bits to be sent when data is requested. The G1
mode causes only data from the ports programmed as inputs to be sent when data is
requested. The G2 mode causes only data from ports programmed as outputs to be
returned when data is requested.
If all ports are programmed as outputs with G1 selected and data is requested,
nothing will be transmitted. Conversely, nothing will be transmitted with all ports
programmed as inputs and G2 selected.
G0 Input and output port data is output
G1 Only input port data is output
G2 Only output port data is output
Example:
@ reset the Digital232
P0C1 configure port 1 as input, ports 2-5 as output
G1 select only input ports when data is requested
R0 read data from the Digital232 input ports
display shows 000000FF (data is dependent
on what is connected to the input)
G2 select output ports when data is requested
R0 read data from the Digital232 input ports
display shows 00 (outputs default to 0)