Avery Berkel CX20 SERIES, Service Manual

Page: 216 / 353

22 — Communications Controller
22–3 CX20/CX30/CX34 Service Manual
22.1 Description
IMPORTANT:
On systems fitted with a communications controller (comms
PCB), if the master machine fails it is essential that the
slaves/satellites are placed in to local mode and NOT powered
down and made stand alone.
NOTE 1: The communications controller is sometimes referred to as the data
processing engine (DPE).
NOTE 2: On systems using communications controllers, when a slave is
disconnected it will reset the service system configuration on power
up to show no communications controller fitted.
The communications controller (comms PCB) is an optional extra. When fitted,
it supplies the current source for the system and controls the ISC and
Host/Master communications interface, storing and totalising all transactions
occurring on the system.
The comms PCB utilises an 8MHz microprocessor with an 8 or 16 bit external
data bus. It can be fitted to one or more scales and communicates via three
bi–directional serial channels:
a) The Avery Berkel interscale communications multidrop network (ISC)
current loop. (The ISC channel is always present on comms PCB.)
b) An RS232 channel. This allows point–to–point Host/Master channel or
interface.
c) A Host master current loop network comprising up to 32 sub–masters.
NOTE: Options b) and c) are mutually exclusive.
The comms PCB is powered by the host machine’s power supply. The power
monitor and ISC signals are on a single connector from the main PCB. The
comms PCB provides its own battery back–up supply for its data RAM.
The following power supplies enter the comms PCB via PL1:
Voltage Current
+12VI 50mA maximum
–12VI 50mA maximum
0VI
+10VI (Unregulated) 750mA maximum
–10VI (Unregulated) 300mA maximum
The comms PCB has a 7805, 5V regulator (VR2) to p5VD for the main
logic supply and a 7805 regulator (VR1) which pr5VI for use in the
RS232 interface.