93LC66A/B

DS21209A-page 6

Preliminary

© 1997 Microchip Technology Inc.

3.6

ERASE/WRITE Disable and Enable

(EWDS/EWEN)

The 93LC66A/B powers up in the ERASE/WRITE Dis-

able (EWDS) state. All programming modes must be

preceded by an ERASE/WRITE Enable (EWEN)

instruction. Once the EWEN instruction is executed,

programming remains enabled until an EWDS instruc-

tion is executed or Vcc is removed from the device. To

protect against accidental data disturbance, the EWDS

instruction can be used to disable all ERASE/WRITE

functions and should follow all programming opera-

tions. Execution of a READ instruction is independent

of both the EWDS and EWEN instructions.

3.7

READ

The READ instruction outputs the serial data of the

addressed memory location on the DO pin. A dummy

zero bit precedes the 8-bit (93LC66A) or 16-bit

(93LC66B) output string. The output data bits will toggle

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

when CS is held high. The memory data will automati-

cally cycle to the next register and output sequentially.

FIGURE 3-4:

EWDS TIMING

FIGURE 3-5:

EWEN TIMING

FIGURE 3-6:

READ TIMING

CS

CLK

DI

1

0

0

0

0

X

•••

X

1

X

CS

CLK

DI

0

0

1

1

X

•••

CS

CLK

DI

DO

1

1

0

An

•••

A0

HIGH-Z

0

Dx

•••

D0

Dx

•••

D0

•••

Dx

D0