UPD75238GJ NEC [NEC], UPD75238GJ Datasheet - Page 130
UPD75238GJ
Manufacturer Part Number
UPD75238GJ
Description
4 BIT SINGLE-CHIP MICROCOMPUTER
Manufacturer
NEC [NEC]
Datasheet
1.UPD75238GJ.pdf
(190 pages)
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(10) Key scan registers (KS0, KS1, and KS2)
(11) Key scan flag (KSF)
The key scan registers (KS0, KS1, and KS2) set segment output data on the key scan timing that is mapped
to display data memory locations (1FCH, 1FDH, 1FEH, 1FFH, 1BEH, and 1BFH).
KS0, KS1, and KS2 are 8-bit registers, which are usually manipulated with an 8-bit manipulation
instruction. (One-bit or 4-bit manipulation is also possible for the lower 4 bits.)
The data set in KS0, KS1, and KS2 is output on the segment output pins on the key scan timing. During
the key scan timing, the rewriting of KS0, KS1, and KS2 is immediately reflected in segment output data,
which can be used for key scanning.
The key scan flag (KSF) is set to 1 on the key scan timing, and is automatically reset to 0 on any other
timing. KSF is mapped to bit 3 at address F8AH, and can be tested on a single-bit basis. KSF cannot
be written to. Testing this flag can determine whether the key scan timing is present, so that the validity
of key input data can be determined.
PD75238
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