uPD789871 Subseries 8-Bit Single-Chip Microcontrollers PUM
uPD789871 Subseries 8-Bit Single-Chip Microcontrollers PUM
uPD789871 Subseries 8-Bit Single-Chip Microcontrollers PUM
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
11.1 VFD Controller/Driver Functions<br />
CHAPTER 11 VFD CONTROLLER/DRIVER<br />
The on-chip VFD controller/driver of the µPD789871 <strong>Subseries</strong> has the following functions.<br />
(1) Can output display signals (DMA operation) by automatically reading display data.<br />
(2) The pins not used for VFD display can be used as I/O port or output port pins (FIP9 to FIP24 pins only).<br />
(3) Luminance can be adjusted in 8 steps by VFD display mode register 1 (DSPM1).<br />
(4) Hardware for key scan application<br />
• Generates an interrupt signal (INTKS) indicating key scan timing.<br />
• Timing in which key scan data is output can be detected by key scan flag (KSF).<br />
• Whether key scan timing is inserted or not can be selected.<br />
(5) High-tolerance output buffer that can directly drive VFD<br />
(6) The FIP17 to FIP24 pins can be connected to pull-down resistors (connected to VLOAD) using mask option (mask<br />
ROM version only). The µPD78F9872 does not have on-chip pull-down resistors).<br />
Of the 25 VFD output pins of the µPD789871 <strong>Subseries</strong>, FIP9 to FIP24 are alternate function pins with port function.<br />
FIP0 to FIP8 are output-only pins.<br />
FIP9 to FIP24 can be used as port pins when VFD display is disabled by bit 7 (DSPEN) of the display mode register<br />
0 (DSPM0). Even when VFD display is enabled, the VFD output pins not used for display signal output can be used<br />
as port pins.<br />
Table 11-1. VFD Output Pins and Alternate-Function Pins for Ports<br />
FIP Pin Name Multiplexed Port Name I/O<br />
FIP9 to FIP16 P97 to P90 Output-only port<br />
FIP17 to FIP24 P87 to P80 I/O port<br />
104 Preliminary User’s Manual U14938EJ1V0UM
Change language