M37544 Datasheet, PDF (33/68 Pages) Renesas Technology Corp – SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

7544 Group
Reset Circuit
The microcomputer is put into a reset status by holding the RE-
SET pin at the “L” level for 2 µs or more when the power source
voltage is 4.5 to 5.5 V and XIN is in stable oscillation. _{______}
After that, this reset status is released by returning the RESET pin
to the “H” level. The program starts from the address having the
contents of address FFFD16 as high-order address and the con-
tents of address FFFC16 as low-order address.
In the case of f(φ) ≤ 8 MHz, the reset input voltage must be 0.9 V
or less when the power source voltage passes 4.5 V.
RESET
Power source
VCC ^voltage
0V
Reset input
voltage
0V
Poweron
(Note)
0.2 VCC
Note : Reset release voltage Vcc 4.5V
RESET
VCC
Power source
voltage
detection circuit
Fig. 37 Example of reset circuit
Clock from
on-chip oscillator
RING
φ
RESET
RESETOUT
SYNC
Address
Data
?
?
?
?
?
?
?
?
?
FFFC FFFD ^ADH,ADL
?
ADL
ADH
Reset address from the
vector table
8-13 clock cycles
Notes _{1 : An on-chip oscillator applies about RING•2 MHz, φ•250 kHz frequency clock}
at average of Vcc = 5 V.
2 : The mark “?” means that the address is changeable depending on the previous state.
3 : These are all internal signals except RESET.
Fig. 38 Timing diagram at reset
Rev.1.04 2004.06.08 page 33 of 66
REJ03B0012-0104Z