Key Scan Flag And Key Scan Data; Key Scan Flag; Key Scan Data - NEC mPD780208 Subseries User Manual

15.7 Key Scan Flag and Key Scan Data

15.7.1 Key scan flag

The key scan flag (KSF) is set to 1 during the key scan timing and reset automatically to 0 during the display
timing.
KSF is mapped at bit 7 of display mode register 0 (DSPM0) and can be tested one bit at a time. It cannot be
written.
By testing the KSF, it can be determined if it is during the key scan timing and if the data input using keys is
correct.

15.7.2 Key scan data

The data stored in ports 8, 9, 10, 11, and 12 are output from pins FIP13 to FIP52 at the key scan timing.
By changing the data output from ports 11 and 12 during the key scan timing, key scan can be performed using
these pins FIP13 to FIP52.
Caution If, during the key scan timing, scanning is performed which causes both the segment and digit
lines to turn ON at the same time, the display may be disturbed.
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CHAPTER 15 VFD CONTROLLER/DRIVER
User's Manual U11302EJ4V0UM