upd178016 Renesas Electronics Corporation., upd178016 Datasheet - Page 65

• Manufacturer Part Number: upd178016
• Description: 8-bit Single-chip Microcontroller
• Manufacturer: Renesas Electronics Corporation.

6. DESCRIPTION OF PD16431A CONTROL
6.1
(1) Detecting a pressed key
(2) Detecting the release of a key
The PD178016GC-051 uses the PD16431A to control the LCD display.
The connection of the PD178016GC-051 to the PD16431A is illustrated below.
Key scan using the PD16431A is performed as follows:
The controller judges the state of the KEYREQ pin (pin 6) of the PD16431A 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).
When a key is released, the level of the KEYREQ pin of the PD16431A 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.
Key Scan
PD178016GC-051
LCD_DAT
LCD CLK
LCD STB
LCD OFF
KEYREQ
37
38
39
40
41
Key request
Strobe
Clock
Data
11
8
7
9
6
STB
OE
DATA
SCK
KEYREQ
PD16431A
PD178016GC-051
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