UPD780204 Datasheet, PDF (42/418 Pages) NEC – 8-Bit Single-Chip Microcontrollers

CHAPTER 2 PIN FUNCTIONS
2.2.12 VLOAD
This is the pull-down resistor connection pin of the VFD controller/driver.
2.2.13 AVREF
The A/D converter’s reference voltage should be input from this pin.
2.2.14 AVDD
This pin supplies power for A/D converter operations.
Always make this pin the same potential as the VDD pin even if the A/D converter is not used.
2.2.15 AVSS
This pin is the ground for the A/D converter.
Always make this pin the same potential as the VSS pin even if the A/D converter is not used.
2.2.16 RESET
This is an active-low system reset input pin.
2.2.17 X1 and X2
These are crystal resonator connection pins for main system clock oscillation.
For external clock supply, input the clock to X1 and its inverted signal to X2.
2.2.18 XT1 and XT2
These are crystal resonator connection pins for subsystem clock oscillation.
For external clock supply, input the clock to XT1 and its inverted signal to XT2.
2.2.19 VDD
This is the positive power supply pin.
2.2.20 VSS
This is the ground potential pin.
2.2.21 VPP (µPD78P0208 only)
A high-voltage should be applied to this pin during PROM programming mode setting and in program write/verify
mode. Connect directly to VSS in normal operation mode.
2.2.22 IC (mask ROM version only)
The IC (Internally Connected) pin sets a test mode in which the µPD780204, 780204A, 780205, 780205A, 780206,
and 780208 are tested before shipment. In normal operation mode, connect the IC pin directly to the VSS pin with
as short a wiring length as possible.
If there is a potential difference between the IC and VSS pins because the wiring length between the IC and VSS
pins is too long, or external noise is superimposed on the IC pin, the user program may not run correctly.
• Directly connect the IC pin to the VSS pin.
VSS IC
Keep the wiring length as short as possible.
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User’s Manual U11302EJ4V0UM