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DS21130C-page 6

Preliminary

© 1996 Microchip Technology Inc.

3.0

DEVICE OPERATION

3.1

READ

The READ instruction outputs the serial data of the

addressed memory location on the DO pin. A dummy

zero bit precedes the 16 bit (x16 organization) or 8 bit

(x8 organization) output string. The output data bits will

toggle on the rising edge of the CLK and are stable after

sible when CS is held high and clock transitions con-

tinue. The memory address pointer will automatically

increment and output data sequentially.

3.2

ERASE

The ERASE instruction forces all data bits of the spec-

ified address to the logical “1” state. The self-timed pro-

gramming cycle is initiated on the rising edge of CLK as

the last address bit (A0) is clocked in. At this point, the

CLK, CS, and DI inputs become don’t cares.

The DO pin indicates the READY/BUSY status of the

device if the CS is high. The READY/BUSY status will

be displayed on the DO pin until the next start bit is

received as long as CS is high. Bringing the CS low will

place the device in standby mode and cause the DO pin

to enter the high impedance state. DO at logical “0” indi-

cates that programming is still in progress. DO at logical

“1” indicates that the register at the specified address

has been erased and the device is ready for another

instruction.

The ERASE cycle takes 3 ms per word (Typical).

3.3

WRITE

The WRITE instruction is followed by 16 bits (or by 8

bits) of data to be written into the specified address.

The self-timed programming cycle is initiated on the ris-

ing edge of CLK as the last data bit (D0) is clocked in.

At this point, the CLK, CS, and DI inputs become don’t

cares.

The DO pin indicates the READY/BUSY status of the

device if the CS is high. The READY/BUSY status will

be displayed on the DO pin until the next start bit is

received as long as CS is high. Bringing the CS low will

place the device in standby mode and cause the DO pin

to enter the high impedance state. DO at logical “0” indi-

cates that programming is still in progress. DO at logical

“1” indicates that the register at the specified address

has been written and the device is ready for another

instruction.

The WRITE cycle takes 3 ms per word (Typical).

3.4

Erase All (ERAL)

The ERAL instruction will erase the entire memory

array to the logical “1” state. The ERAL cycle is identical

to the ERASE cycle except for the different opcode. The

ERAL cycle is completely self-timed and commences

on the rising edge of the last address bit (A0). Note that

the least significant 8 or 9 address bits are don’t care

bits, depending on selection of x16 or x8 mode. Clock-

ing of the CLK pin is not necessary after the device has

entered the self clocking mode. The ERAL instruction is

guaranteed at Vcc = +4.5V to +6.0V.

The DO pin indicates the READY/BUSY status of the

device if the CS is high. The READY/BUSY status will

be displayed on the DO pin until the next start bit is

received as long as CS is high. Bringing the CS low will

place the device in standby mode and cause the DO pin

to enter the high impedance state. DO at logical “0” indi-

cates that programming is still in progress. DO at logical

“1” indicates that the entire device has been erased and

is ready for another instruction.

The ERAL cycle takes 15 ms maximum (8 ms typical).

3.5

Write All (WRAL)

The WRAL instruction will write the entire memory array

with the data specified in the command. The WRAL

cycle is completely self-timed and commences on the

rising edge of the last address bit (A0). Note that the

least significant 8 or 9 address bits are don’t cares,

depending on selection of x16 or x8 mode. Clocking of

the CLK pin is not necessary after the device has

entered the self clocking mode. The WRAL command

does include an automatic ERAL cycle for the device.

Therefore, the WRAL instruction does not require an

ERAL instruction but the chip must be in the EWEN sta-

tus. The WRAL instruction is guaranteed at Vcc = +4.5V

to +6.0V.

The DO pin indicates the READY/BUSY status of the

device if the CS is high. The READY/BUSY status will

be displayed on the DO pin until the next start bit is

received as long as CS is high. Bringing the CS low will

place the device in standby mode and cause the DO pin

to enter the high impedance state. DO at logical “0” indi-

cates that programming is still in progress. DO at logical

“1” indicates that the entire device has been written and

is ready for another instruction.

The WRAL cycle takes 30 ms maximum (16 ms typ-

ical).