RCH
INSTALLATION AND MAINTENANCE MANUAL model TOUCH ME
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9.2 DISPLAY CIRCUIT
The two DISPLAY MODULES, operator and customer, are controlled in parallel by the LCD
D0–D3 lines. The EN1 and EN2 signals respectively control the CLERCK display and the
CUSTOMER display. The displays are fed with 5VDC directly by the CPU card, and are
both equipped with 5VCC retro-lighting controlled by the microprocessor (X1); it is possible
to disable the customer display’s retro-lighting by removing an apposite jumper (J1).
Contrast can be regulated independently for both displays: CONTRLV for the Operator’s
display and CONTRLC for the Customer’s display respectively control the base of the
BC807 (Q4) and (Q5) transistors.
The pilot signals of the dot matrix (corresponding to the characters of the displays) LCD
D0-D3 are generated by the CPU (X1) through the ports P73,P75,P93,P94.
Connection control of both connectors of each display is guaranteed by a firmware routine
that verifies that the display is available for reading (lines R/W and LCD D0-D3).
