UPD75518 NEC, UPD75518 Datasheet - Page 131

• Manufacturer Part Number: UPD75518
• Description: 4 BIT SINGLE-CHIP MICROCOMPUTER
• Manufacturer: NEC

(3) Configuration of INT2 and KR0 to KR7 (key interrupt) pins
Fig. 5-4 shows the configuration of INT2 and KR0 to KR7. IRQ2 is set in one of the following modes with
the edge detection mode register (IM2):
(a) Detection of a rising edge of the INT2 pin input
(b) Detection of a falling edge of one of the KR0 to KR7 pin inputs (key interrupt)
When a rising edge of the INT2 pin input is detected, IRQ2 is set.
One of the pins KR0 to KR7 is selected to be used for interrupt input with the edge detection mode
register (IM2). When a falling edge of one of input signals applied to the selected pin is detected, IRQ2
is set.
Fig. 5-3 (c) shows the format of IM2. A 4-bit memory manipulation instruction is used to set IM2. A
RESET signal occurrence clears all bits to 0, and a rising edge is selected for INT2.
Example If KR4 to KR7 are selected, and the level of signals input to KR4 to KR7 are all high, a falling
Caution If any of the selected pins has been input a low-level signal, a falling edge appearing on
another pin does not set IRQ2.
edge appearing on any one of these inputs sets IRQ2.
PD75518(A)
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