Chapter 3
Operation of the GPIB-232CV-A
©
National Instruments Corporation
3-7
C Mode Overview
In C mode, the GPIB-232CV-A and a serial device together act as the GPIB
System Controller. Figure 3-5 shows the C mode system layout.
Figure 3-5.
C Mode System Layout
When you turn the power on with the GPIB-232CV-A in C mode, the
GPIB-232CV-A asserts IFC* for 500 µs and addresses the instruments to
listen. On a GPIB system, asserting IFC* for at least 100 µs initializes the
GPIB and causes the System Controller to become Controller-In-Charge
(CIC).
After the GPIB-232CV-A becomes CIC, it sends out the GPIB listen
address indicated by SW1 switches 1 through 5. If switches 1 through 5 are
all ON, no addressing is performed. This configuration is useful if you are
talking to a listen-only device that does not require addressing. The
GPIB-232CV-A always asserts REN* when addressing other devices.
Data Transfers in C Mode
All incoming serial data to the GPIB-232CV-A is stored in an internal data
buffer until it is accepted by the GPIB device. All GPIB data sent to the
GPIB-232CV-A is passed immediately to the serial port without being
buffered. You can send data to your serial port as if you had a serial device
connected to it. The data is converted and sent to the GPIB instrument.
When the instrument has data to send back, the GPIB-232CV-A addresses
the instrument to talk and passes all received data to the RS-232 port.
GPIB-232CV-A
GPIB
Device
PO
WER
READ
Y
TALK LISTEN
B
USY
FULL
GPIB-232CV-A
FUSE
Serial
Device
GPIB Controller
