93AA76A/B/C, 93LC76A/B/C, 93C76A/B/C
DS21796D-page 8 2004 Microchip Technology Inc.
2.6 ERASE/WRITE DISABLE And ENABLE (EWDS/EWEN)
The 93XX76A/B/C powers up in the ERASE/WRITE
Disable (EWDS) state. All programming modes must be
precede d by an ERASE/WRITE En able (EWEN) instruc-
tion. Once the EWEN instruction is executed, program-
ming remains enabled until an EWDS instruction is
executed or V
CC 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
operations. Execution of a READ instruction is
independent of both the EWEN and EWDS instructions.
FIGURE 2-3: EWDS TIMING
FIGURE 2-4: EWEN T IMIN G
2.7 READ
The READ instruction outputs the serial data of the
addressed memory location on the DO pin. A dummy
zero bit prece des the 8-bit (If ORG pin is low or A-V ersion
devices) or 16-bit (If ORG pin is high or B-version
devic es) ou tput st ring. The ou tput dat a bi ts will toggle on
the rising edge of the CLK and are stable after the spec-
ified time dela y (T
PD). Sequ enti al r ead is possi ble w hen
CS is held high. The memory data will automatically cycle
to t he ne xt re gi ster an d o utput s eq ue nt ia ll y.
FIGU RE 2- 5 : READ TIMIN G
CS
CLK
DI
10
000X
•••
X
T
CSL
1X
CS
CLK
DI
00 1 1X
TCSL
•••
CS
CLK
DI
DO
110
An
•••
A0
HIGH-Z
0Dx
•••
D0 Dx
•••
D0
•••
Dx D0
