PCM-2 Manual.pdf - Voss Associates

09 Output bit 1 @ A003Dispiay 1 clock
10 Output bit 0 @ A003Dispiay 1 data
11 +5 Volts to displays
12 Ground
Connector P13: Spare keypad inputs
Pinout: 01 Row 3 drive
02 Row 2 drive
03 Column 1 sense
04 Row 1 drive
05 Row 0 drive
Keyboard Inputs
A matrix-encoded keypad of up to 20 keys may be connected to the Front Panel
Board at connector PI0.
Host Communications Port Configuration
Eberline's SP24 series front panel boards (based on PCB PIN 11526) provide
three serial communications ports, one of which is normally used for
communications with a site host computer. When the host provides one port per
instrument, RS-232 levels are normally used. If multiple instruments are
connected in party line network, it is necessary to use RS-485 levels.
Host communications are supported through connector P3 on the SP24 board, a 9­
pin female "D" connector. In the RS-232 configuration, IC An provides serial
data output on pin 3 of this connector and receives input data on pin 2. DTR out
is present on pin 4 and DSR in is present on pin 6. When the SP24 is configured
for RS-485, IC A29 is used. P3 pin 1 is the positive I/O line and pin 9 is
negative. Connector pin 5 is ground.
Reconfiguration
Procedure
To convert an RS-232 board to RS-485, remove the IC from location A27 and
install an RS-485 transceiver chip in the socket at A29. The preferred chip for
this application is a Linear Technology LTC485CN8 (Eberline PIN ICCMA485).
A National Semiconductor DS3695N may also be used at the cost of increased
power consumption.
Converting an RS-485 board to RS-232 is the opposite; remove IC A29 and
install a Maxim MAX233CPP (Eberline PIN ICXXMAX2323) at A27.
Do not simultaneously install A27 and A29.
PCM2.MANI REV AI April 1995 11 -7