UPD784938 Datasheet, PDF (657/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 26 RESET FUNCTION
26.1 Reset Function
When low level is input to the RESET input pin, a system reset is affected, the various hardware units are set to the
states shown in Table 26-2, and all pins except the power supply pins and the X1 and X2 pins are placed in the high-
impedance state. Table 26-1 shows the pin statuses on reset and after reset release.
When the RESET input changes from low to high level, the reset state is released, the contents of address 00000H of
the reset vector table are set in bits 0 to 7 of the program counter (PC), the contents of address 00001H in bits 8 to 15,
and 0000B in bits 16 to 19, a branch is made, and program execution is started at the branch destination address. A reset
start can therefore be performed from any address in the base area.
The contents of the various registers should be initialized as required in the program in the base area.
To prevent misoperation due to noise, the RESET input pin incorporates an analog delay noise elimination circuit (see
Figure 26-1).
Figure 26-1. Reset Signal Acknowledgment
Delay
Delay
Execution of instruction
Delay PC initialization, etc. _{at reset start address}
RESET
(input)
Internal reset signal
Reset start Reset end
Preliminary User’s Manual U13987EJ1V0UM00
657