93LC66A Datasheet, PDF (6/12 Pages) Microchip Technology – 4K 2.5V Microwire Serial EEPROM

93LC66A/B
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.
FIGURE 3-4: EWDS TIMING
CS
CLK
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 tog-
gle on the rising edge of the CLK and are stable after
the specified time delay (TPD). Sequential read is pos-
sible when CS is held high. The memory data will auto-
matically cycle to the next register and output
sequentially.
TCSL
DI
1
0
0
0
0
X
•••
X
FIGURE 3-5: EWEN TIMING
TCSL
CS
CLK
DI
1
0
0
1
1
X
•••
X
FIGURE 3-6: READ TIMING
CS
CLK
DI
DO
1
1 0 An ••• A0
HIGH-Z
0
Dx ••• D0 Dx ••• D0 Dx ••• D0
DS21209C-page 6
 1998 Microchip Technology Inc.