INFICON RQCM - Quartz Crystal Microbalance Research System - Manual (Page 78)

RQCM – RESEARCH QUARTZ CRYSTAL MICROBALANCE
COMPUTER INTERFACE 7-2
The RQCM acts as DTE, and accordingly the 9-pin connector has ‘plug’ pins. It can be used
with a DCE or a DTE host cable connection providing the sense of the RxD/TxD data lines and
the control lines is observed. Pin 2 ‘TxD’ transmits data from the RQCM to the host; pin 3
‘RxD’ receives data from the host. Pin 7 ‘CTS’ is a control output signal, and pin 8 ‘RTS’ is a
control input signal.
In this implementation, pin 7 ‘CTS’ means what is says, namely, this is an output control line,
and when the RQCM asserts this control line ‘true’ the host can transmit to the RQCM. On the
other hand, pin 8 ‘RTS’ is not quite what it may seem because this is a signal input to the RQCM,
and it is intended that the host should assert this line ‘true’ only when the RQCM is allowed to
transmit data to the host. The RQCM does not generate an RTS ‘request-to-send’ as such for the
host PC, so the host should assert pin 8 true whenever the RQCM is allowed to transmit to the
host, without being asked to do so.
The RQCM’s RS-232 port is automatically set up to operate with the following specifications:
19200 Baud, 8 Bit data, No Parity, 1 Stop bit
Figure 28 D9S DTE Rear-panel RS-232 socket connector
Pin Signal
Number RS-232 RS-485
1 Not used Rx- Input
2 Tx Output Rx+ Input
3 Rx Input Tx+ Output
4 Not used Tx- Output
5 GND GND
6 Not used CTS- Input
7 CTS Input CTS+ Input
8 RTS Output RTS+ Output
9 Not used RTS- Output
Table 7-1 D9 Rear Panel RS-232/RS-485 Connector Pin Assignments
7.6 RS-485 SERIAL INTERFACE
The optional RS-485 serial interface of the RQCM allows connection of up to 32 separate devices
equipped with RS-485. The RS-485 serial interface is also ideal in electrically noisy
environments and in applications where long cables are required. The RS-485 port of the RQCM
is the same D9P connector on the rear panel used for RS-232. The pin layout is shown in Figure
28 and Table 7-1lists the pin signal assignments, including a definition of whether the signal is an
input or an output of the RQCM.
The RQCM’s RS-485 port is automatically set up to operate with the following specifications:
19200 Baud, 8 Bit data, No Parity, 1 Stop bit