4-5
4
4.2.3
4863 OEM BOARD DIFFERENCES
Versions of the 4863 OEM Board have an additional serial interface as
shown in Figure 4-2. The serial interface has both RS-232 and RS-485
capability. The RS-232 is a full duplex interface with transmit and receive
signals. There are no handshaking lines because of the short string lengths
of the 4863 commands and responses. The RS-485 (RS-422) is a half duplex
interface with a and - signal pair. The transmitter is only enabled
when the 4863 is responding to a query. Pullup and pulldown resistors are
provided to bias the RS-485 signals into the logic 1 or mark state and avoid
receiver errors.
When the serial interfaces are installed, they are activated at power turn-on
and remain active until the unit is addressed on the GPIB interface and put
into the Remote state. The serial parameters default to 9600 baud, 8 data
bits, no parity and one stop bit. The 4863 detects which serial input is being
used and directs query responses back on the appropriate interface.
Extra digital inputs are provided on the OEM board to read a GPIB address
from an external address switch. The address inputs are low true contact
closures to ground.
Extra digital inputs are provided on the OEM board to read a GPIB address
from an external address switch. The address inputs are low true contact
closures to ground.
