93LCS56_04 Datasheet, PDF (5/14 Pages) Microchip Technology – 2K/4K 2.5V Microwire Serial EEPROM with Software Write Protect

The DO pin indicates the READY/BUSY status of the
device if CS is brought high after a minimum of 250 ns
(TCSL) and before the entire write cycle is complete. DO
at logical “0” indicates that programming is still in
progress. DO at logical “1” indicates that the register at
the specified address has been written with the data
specified and the device is ready for another instruc-
tion. WRITE instruction is valid only if specified address
is unprotected.
The WRITE cycle takes 4 ms per word typical.
2.8 Erase All (ERAL)
The ERAL instruction will erase the entire memory
array to the logical “1”. The ERAL cycle is identical to
the ERASE cycle except for the different opcode. The
ERAL cycle is completely self-timed and commences
at the falling edge of the CS. PE pin MUST be held
“high” while loading the instruction but becomes “don't
care” thereafter. Clocking of the CLK pin is not neces-
sary after the device has entered the self clocking
mode. The ERAL instruction is guaranteed at VCC = 4.5
to 6V and valid only when Protect Register is cleared.
The DO pin indicates the READY/BUSY status of the
device if CS is brought high after a minimum of 250 ns
low (TCSL) and before the entire write cycle is complete.
The ERAL cycle takes 15 ms maximum (8 ms typical).
2.9 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
at the falling edge of the CS. PE pin MUST be held
“high” while loading the instruction but becomes “don't
care” thereafter. Clocking of the CLK pin is not neces-
sary 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 status. The WRAL instruc-
tion is guaranteed at VCC = 4.5 to 6V and valid only
when Protect Register is cleared.
The DO pin indicates the READY/BUSY status of the
device if CS is brought high after a minimum of 250 ns
low (TCSL).
The WRAL cycle takes 30 ms maximum (16 ms typi-
cal).
Note:
In order to execute either READ, EWEN,
ERAL, WRITE, WRAL, or EWDS instruc-
tions, the Protect Register Enable (PRE)
pin must be held LOW.
93LCS56/66
2.10 Protect Register Read (PRREAD)
The Protect Register Read (PRREAD) instruction out-
puts the address stored in the Protect Register on the
DO pin. The PRE pin MUST be held HIGH when load-
ing the instruction and remains HIGH until CS goes
LOW. A dummy zero bit precedes the 8-bit output
string. The output data bits in the memory Protect Reg-
ister will toggle on the rising edge of the CLK as in the
READ mode.
2.11 Protect Register Enable (PREN)
The Protect Register Enable (PREN) instruction is
used to enable the PRCLEAR, PRWRITE, and PRDS
modes. Before the PREN mode can be entered, the
device must be in the EWEN mode. Both PRE and PE
pins MUST be held “high” while loading the instruction.
The PREN instruction MUST immediately precede a
PRCLEAR, PRWRITE, or PRDS instruction.
2.12 Protect Register Clear (PRCLEAR)
The Protect Register Clear (PRCLEAR) instruction
clears the address stored in the Protect Register and,
therefore, enables all registers for programming
instructions such as ERASE, ERAL, WRITE, and
WRAL. The PRE and PE pin MUST be held HIGH
when loading the instruction. Thereafter, PRE and PE
pins become “don't care”. A PREN instruction must
immediately precede a PRCLEAR instruction.
2.13 Protect Register Write (PRWRITE)
The Protect Register Write (PRWRITE) instruction
writes into the Protect Register the address of the first
register to be protected. After this instruction is exe-
cuted, all registers whose memory addresses are
greater than or equal to the address pointer specified in
the Protect register are protected from any program-
ming instructions. Note that a PREN instruction must
be executed before a PRWRITE instruction and, the
Protect Register must be cleared (by a PRCLEAR
instruction) before executing the PRWRITE instruction.
The PRE and PE pins MUST be held HIGH while load-
ing PRWRITE instruction. After the instruction is
loaded, they become “don't care”.
2.14 Protect Register Disable (PRDS)
The Protect Register Disable (PRDS) instruction is a
ONE TIME ONLY instruction to permanently set the
address specified in the Protect Register. Any attempts
to change the address pointer will be aborted. The PRE
and PE pins MUST be held HIGH while loading PRDS
instruction. After the instruction is loaded, they become
“don't care”. Note that a PREN instruction must be exe-
cuted before a PRDS instruction.
 2004 Microchip Technology Inc.
DS11181E-page 5