93LC46A/B

DS21173E-page 6

 2000 Microchip Technology Inc.

3.6

ERASE/WRITE Disable and Enable

(EWDS/EWEN)

The 93LC46A/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 EWEN and EWDS 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 (93LC46A) or 16-bit

(93LC46B) output string. The output data bits will tog-

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

sible when CS is held high. The memory data will auto-

matically 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

10

00

0

X

•••

X

1X

CS

CLK

DI

00

1

1

X

•••

CS

CLK

DI

DO

11

0

An

•••

A0

HIGH-Z

0Dx

•••

D0

Dx

•••

D0

•••

Dx

D0