UPD784044 Datasheet, PDF (51/90 Pages) NEC – 16-BIT SINGLE-CHIP MICROCONTROLLER

µPD784044(A), 784046(A)
11. RESET FUNCTION
When a low level is input to the RESET pin, the internal hardware is initialized (reset status).
When the RESET signal goes high, the following data is set to the program counter (PC).
• Lower 8 bits of PC : contents of address 0000H
• Middle 8 bits of PC : contents of address 0001H
• Higher 4 bits of PC : 0
The contents of the PC are assumed as a branch destination address and program execution is started from
this address. Therefore, the program can be reset and started from any address.
Set the contents of each register by program as necessary.
To prevent malfunctioning due to noise, a noise rejection circuit is provided to the RESET input circuit. This
noise rejection circuit is a sampling circuit with analog delay.
Figure 11-1. Accepting Reset
RESET
(input)
Delay
Delay
Delay
Instruction execution
PC initialization _{at reset start address}
Internal reset signal
Reset starts
Reset ends
Keep the RESET signal active until the oscillation stabilization time (about 40 ms) elapses when executing
a reset operation on power application or when releasing the STOP mode by reset.
Figure 11-2. Reset Operation on Power Application
Oscillation stabilization time
Delay Initializes PC Instruction execution at reset start address
VDD
RESET
(input)
Internal reset signal
Reset ends
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