PD178016GC-051_15 Datasheet, PDF (67/96 Pages) Renesas Technology Corp – 8-BIT SINGLE-CHIP MICROCONTROLLER WITH BUILT-IN PRESCALER, PLL FREQUENCY SYNTHESIZER, AND IF COUNTER FOR AUTOMOTIVE FM/MW/LW RADIO APPLICATIONS

µPD178016GC-051
6. DESCRIPTION OF µPD16431A CONTROL
The µPD178016GC-051 uses the µPD16431A to control the LCD display.
The connection of the µPD178016GC-051 to the µPD16431A is illustrated below.
µ PD178016GC-051
µ PD16431A
LCD_DAT 37
LCD CLK 38
LCD STB ³⁹
Data
Clock
Strobe
8 DATA
7 SCK
9 STB
LCD OFF 40
KEYREQ 41
Key request
11 OE
6 KEYREQ
6.1 Key Scan
Key scan using the µPD16431A is performed as follows:
(1) Detecting a pressed key
The controller judges the state of the KEYREQ pin (pin 6) of the µPD16431A every 20 ms.
When the KEYREQ pin is high, it is assumed that a key is being pressed. Noise elimination (chattering
elimination) based on three consecutive matches is applied.
When noise elimination is performed correctly, the key code is read with serial reception.
Key data is received within 20 ms while a key is held down (the KEYREQ pin is high).
(2) Detecting the release of a key
When a key is released, the level of the KEYREQ pin of the µPD16431A goes from high to low. The pin is scanned
every 20 ms and, if the low level is detected three times in a row, it is judged that the key has been released.
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