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User’s Manual U11302EJ4V0UM
CHAPTER 15 VFD CONTROLLER/DRIVER
15.1 VFD Controller/Driver Functions
The functions of the VFD controller/driver incorporated in the
µ
PD780208 Subseries are as follows.
(1) Automatically outputs the segment signals (DMA operation) and digit signals by automatically reading data
displayed.
(2) Controls 9- to 40-segment and 2- to 16-digit VFDs (vacuum fluorescent display) using display mode registers
0, 1, and 2 (DSPM0 to DSPM2).
(3) Digit signal output timing can be specified freely by selecting display mode 2 using display mode register
0 (DSPM0).
(4) Pins not used for VFD display can be used as output and I/O ports (but FIP0 to FIP12 are display output-
only pins).
(5) Luminance can be adjusted in 8 levels using display mode register 1 (DSPM1).
(6) Incorporates hardware for key scan application.
•
Generates interrupt signal (INTKS) indicating key scan timing.
•
Outputs key scan signals from segment output pins by setting key scan data to port 8 through port 12.
•
Detects timing at which key scan data are output by the key scan flag (KSF).
(7) Incorporates a high-withstanding-voltage output buffer that can directly drive the VFD.
(8) The display output pins can be connected to on-chip pull-down resistors by mask option.
Cautions 1. This cannot be used with the subsystem clock. To stop the main oscillation, stop the
display in advance by setting bits 4 to 7 (DIGS0 to DIGS3) of display mode register 1
(DSPM1) to 0000.
2. Set ports 8 through 12 to 0 and output latches to 0 before doing the following:
• Using the VFD controller/driver
• Stopping display