Power-On Reset Circuit - Star Micronics TSP400 Series Technical Manual

2-4. Power-On Reset Circuit

Immediately following power-on the printer executes a power-on reset, initializing all circuit elements. The power-on
reset serves as protection against operational errors. The power-on RESET signal is maintained for approximately 160ms.
The reset circuit is illustrated below.
+5V
+5V
IC4
VCC
CD RESET
+
GND
C2
RESET IC
1
At power on, voltage-detector circuit IC4 (M51953BL) outputs a LOW signal from its OUT terminal. The signal
lasts for approximately 160ms, as determined by capacitor C2 (0.47 F):
T = 0.34 C2 (pF) [ s] = 160ms
2
The LOW signal resets the CPU and the mechanism drive circuits, and sets S-RAM into backup state.
IC5 : CPU
CPU
RES RESO
DD3
Back-up
Circuit
Fig. 2-10 Power-On Reset Circuit
– 27 –
THEORY OF OPERATION
+5V
+5V
VCC
S-RAM
IC1
IC10
RESET
Gate
array