Rs-232C Communication Considerations - HP 64000 Reference Manual

SYSTEM OVERVIEW MANUAL
MODEL 64000
RS-232-C Communication Considerations
The Model 64000 provides for asynchronous serial communication between the Model 64000
and external communications devices. Communication is controlled by five switches on the
I/O board !first board in the card cagei. Figure 2-35 shows the location of five switches. Table
2-11 shows the required switch positions to evoke the appropriate serial communications.
Switch S1 is set to either 20 mA or 60 mA depending on the requirements of the TTY. The
TTY is connected to the rear panel TTY terminals for half-duplex or full-duplex
communications.
Switch S2 provides for internal receive or transmit clock selection.
Switch S3 selects I LOOP (TTY) or RS-232-C operation. Switch S4 is an 8-bit multifunction
switch. Table 2-12 shows the individual bit functions and the settings required to obtain these
functions.
Bits 2 thru 5 of Switch S5 control the baud rate (see table 2-13). Bit 1 controls the RTS line for
full and half-duplex operation. For half-duplex operation, Bit 1 is set to the off position. The
RTS output is then driven by the USART. For full-duplex operation, Bit 1 is set to the on
position. The RTS line is pulled up to +12V.
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