Star Micronics TSP400 technical manual Power-On Reset Circuit, Theory Of Operation

THEORY OF OPERATION

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.

+

C2

	+5V
IC4	+5V
	VCC
CD	RESET
	GND

RESET IC

IC5 : CPU

CPU

RESRESO

DD3

Back-up

Circuit

+5V

+5V

VCC

S-RAM

IC10

RESET

Gate array

IC1

Fig. 2-10 Power-On Reset Circuit

1At 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 (0.47μF):

T = 0.34 × C2 (pF) [μs] = 160ms

2The LOW signal resets the CPU and the mechanism drive circuits, and sets S-RAM into backup state.

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