GMS77C1001 datasheet(35/44 Pages) HYNIX

35 / 44 page

GMS77C1000/GMS77C1001

July. 2001 Ver. 1.1

14. RESET

GMS77C100X devices may be reset in one of the follow-

ing ways:

- Power-On Reset (POR)

- Power-Fail detect reset (PFDR)

- RESET (normal operation)

- RESET wake-up reset (from SLEEP)

- WDT reset (normal operation)

- WDT wake-up reset (from SLEEP)

Each one of these reset conditions causes the program

counter to branch to reset vector address. (GMS77C1000

is 1FFH and GMS77C1001 is 3FFH ).

Table 14-1 shows these reset conditions for the PCL and

STATUS registers.

Some registers are not affected in any reset condition.

Their status is unknown on POR and unchanged in any

other reset. Most other registers are reset to a “reset state”

on Power-On Reset (POR), PFDR, RESET or WDT reset.

A RESET or WDT wake-up from SLEEP also results in a

device reset, and not a continuation of operation before

SLEEP.

The TO and PD bits (STATUS <4:3>) are set or cleared

depending on the different reset conditions. These bits may

be used to determine the nature of the reset.

Table 14-2 lists a full description of reset states of all reg-

isters. Figure 14-1 shows a simplified block diagram of the

on-chip reset circuit.

Condition

PCL

Addr: 02H

STATUS

Addr: 03H

Power-On Reset

1111 1111

0001 1xxx

RESET reset or PFD

reset (normal operation)

1111 1111

000u uuuu1

1. TO and PD bits retain their last value until one of the other

reset conditions occur.

RESET wake-up or PFD

reset (from SLEEP)

1111 1111

0001 0uuu

WDT reset (normal

operation)

1111 1111

0000 uuuu2

2. The CLRWDT instruction will set the TO and PD bits.

Legend : x = unknown, u = unchanged.

WDT wake-up (from

SLEEP)

1111 1111

0000 0uuu

TABLE 14-1 RESET CONDITIONS FOR SPECIAL

REGISTERS

Address

Power-On

Reset

Wake-up

Reset

RESET, PFDR,

WDT Reset

WN/A

xxxx xxxx

uuuu uuuu

TRIS

N/A

1111 1111

OPTION

N/A

0011 1111

INDF

00H

xxxx xxxx

uuuu uuuu

TMR0

01H

xxxx xxxx

uuuu uuuu

PCL1

02H

1111 1111

STATUS1

03H

0001 1xxx

100q quuu

000q quuu

FSR

04H

1xxx xxxx

1uuu uuuu

PORTA

05H

---- xxxx

---- uuuu

PORTB

06H

xxxx xxxx

uuuu uuuu

General Purpose Register Files

07-1FH

xxxx xxxx

uuuu uuuu

TABLE 14-2 RESET CONDITIONS FOR ALL REGISTERS

1. See Table 14-1 for reset value for specific conditions.

Legend : - = unimplemented, read as ‘0’, x = unknown, u = unchanged.

q = see the tables in Section 17 for possible values.

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