UPD784907 Datasheet, PDF (63/98 Pages) NEC – 16-BIT SINGLE-CHIP MICROCONTROLLER

µPD784907, 784908
12. RESET FUNCTION
When a low-level signal is input to the RESET pin, the internal hardware becomes initialize status (reset status).
When the RESET input makes a low-to-high transition, the following data is loaded into the program counter (PC):
• Low-order 8 bits of the PC: Contents of address 0000H
• Intermediate 8 bits of the PC: Contents of address 0001H
• High-order 4 bits of the PC: 0
The PC contents are used as a branch destination address, and program execution starts from that address.
Therefore, a reset start can be performed from an arbitrary address.
The contents of each register can be set by software, as necessary.
The RESET input circuit incorporates a noise eliminator to prevent malfunctions caused by noise. This noise
eliminator is an analog delay sampling circuit.
Delay
Figure 12-1. Accepting Reset
Delay
Delay
Execute instruction
Initialize PC _{of reset start address}
RESET
(input)
Internal reset signal
Start reset
End reset
For power-on reset, the RESET signal must be held active until the oscillation stabilization time (approximately 40
ms) has elapsed.
Figure 12-2. Power-On Reset
Oscillation stabilization time Delay Initialize PC
Execute instruction of
reset start address
VDD
RESET
(input)
Internal reset signal
End reset
Data Sheet U11680EJ2V0DS00
63