Epson S1C63558 2.2 Initial Reset, 2.2.1 Reset terminal (RESET)

CHAPTER 2: POWER SUPPLY AND INITIAL RESET

2.2 Initial Reset

To initialize the S1C63558 circuits, initial reset must be executed. There are two ways of doing this.

(1)External initial reset by the RESET terminal

(2)External initial reset by simultaneous low input to terminals K00–K03 (mask option setting)

The circuits are initialized by either (1) or (2). When the power is turned on, be sure to initialize using the reset function. It is not guaranteed that the circuits are initialized by only turning the power on.

Figure 2.2.1 shows the configuration of the initial reset circuit.

OSC1	OSC1	1 Hz
	oscillation	Divider 2 Hz
OSC2	circuit
	Mask option
	VDD
K00
K01	Time	Mask option
K02	authorize	Noise	Internal
	circuit	reject
		circuit	initial
K03			reset
	VDD	R Q
RESET		S

Fig. 2.2.1 Configuration of initial reset circuit

2.2.1 Reset terminal (RESET)

Initial reset can be executed externally by setting the reset terminal to a low level (VSS). After that the initial reset is released by setting the reset terminal to a high level (VDD) and the CPU starts operating. The reset input signal is maintained by the RS latch and becomes the internal initial reset signal. The RS latch is designed to be released by a 2 Hz signal (high) that is divided by the OSC1 clock. Therefore in normal operation, a maximum of 250 msec (when fOSC1 = 32.768 kHz) is needed until the internal initial reset is released after the reset terminal goes to high level. Be sure to maintain a reset input of 0.1 msec or more.

However, when turning the power on, the reset terminal should be set at a low level as in the timing shown in Figure 2.2.1.1.

2.2 V

VDD

2.0 msec or more

RESET0.5•VDD

0.1•VDD or less (low level)

Power on

Fig. 2.2.1.1 Initial reset at power on

The reset terminal should be set to 0.1•VDD or less (low level) until the supply voltage becomes 2.2 V or more. After that, a level of 0.5•VDD or less should be maintained more than 2.0 msec.

S1C63558 TECHNICAL MANUAL EPSON 9