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User’s Manual U15017EJ2V0UD
CHAPTER 14 VFD CONTROLLER/DRIVER
14.1 Function of VFD Controller/Driver
The VFD controller/driver of the
μ
PD784976A Subseries has the following functions.
(1) Can output display signals (DMA operation) by automatically reading display data.
(2) The pins not used for VFD display can be used as I/O port or output port pins (FIP16 to FIP47 pins only).
(3) Luminance can be adjusted in 8 steps by display mode register 1 (DSPM1).
(4) Hardware for key scan application
Generates an interrupt signal (INTKS) indicating key scan timing
Timing in which key scan data is output can be detected by key scan flag (KSF).
Whether key scan timing is inserted or not can be selected.
(5) High-voltage output buffer that can directly drive VFD
(6) FIP0 to FIP15 pins are connected to pull-down resistors. FIP16 to FIP47 pins can be connected to pull-down
resistors using a mask option (mask ROM version only). The
μ
PD78F4976A does not have pull-down
resistors).
Of the 48 VFD output pins of the
μ
PD784976A Subseries, FIP16 to FIP47 are multiplexed with port pins. FIP0
to FIP15 are dedicated VFD output pins.
FIP16 to FIP47 can be used as port pins when VFD display is disabled by bit 7 (DSPEN) of display mode register
0 (DSPM0). Even when VFD display is enabled, the VFD output pins not used for display signal output can be used
as port pins.
Table 14-1. VFD Output Pins and Multiplexed Port Pins
VFD Pin Name
Multiplexed Port Name
I/O
FIP16 to FIP23
P70 to P77
I/O port
FIP24 to FIP31
P80 to P87
I/O port
FIP32 to FIP39
P90 to P97
I/O port
FIP40 to FIP47
P100 to P107
Output port