RCH
INSTALLATION AND MAINTENANCE MANUAL model TOUCH ME
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9. CIRCUIT DESCRIPTION
9.1 KEYBOARD CIRCUIT
The keyboard is managed directly by the CPU (X1) through 6 lines ( C-0 – C-5). The
scanning signal is resent to the CPU after pressing one of the keys of the keyboard through
the R0 –R7 lines coded by (X7) 4051 and the decoder (X6) 74hc138.
Pressing one of the keys determines the short circuit of one of the corresponding C0-C5
lines with one of the signal return lines (R0-R7).
The keyboard (with 35 keys) can be easily personalized without opening the device (see
chapter 2.8).