93LCS56_04 Datasheet, PDF (10/14 Pages) Microchip Technology – 2K/4K 2.5V Microwire Serial EEPROM with Software Write Protect

93LCS56/66
FIGURE 2-13: PRDS TIMING
PRE
PE
CS
CLK
TCSL
DI
1
0
0
0 •••
0
0
0
0
8 BITS OF "0"
DO
BUSY
READY
TWC
ONE TIME ONLY instruction. A PREN cycle must immediately precede a PRDS cycle.
3.0 PIN DESCRIPTION
3.1 Chip Select (CS)
A HIGH level selects the device. A LOW level deselects
the device and forces it into standby mode. However, a
programming cycle which is already initiated and/or in
progress will be completed, regardless of the CS input
signal. If CS is brought LOW during a program cycle,
the device will go into standby mode as soon as the
programming cycle is completed.
CS must be LOW for 250 ns minimum (TCSL) between
consecutive instructions. If CS is LOW, the internal
control logic is held in a RESET status.
3.2 Serial Clock (CLK)
The Serial Clock is used to synchronize the communi-
cation between a master device and the 93LCS56/66.
Opcode, address, and data bits are clocked in on the
positive edge of CLK. Data bits are also clocked out on
the positive edge of CLK.
CLK can be stopped anywhere in the transmission
sequence (at HIGH or LOW level) and can be contin-
ued anytime with respect to clock HIGH time (TCDD)
and clock LOW time (TCKL). This gives the controlling
master freedom in preparing opcode, address, and
data.
CLK is a “Don't Care” if CS is LOW (device deselected).
If CS is HIGH, but START condition has not been
detected, any number of clock cycles can be received
by the device without changing its status (i.e., waiting
for START condition).
CLK cycles are not required during the self-timed
WRITE (i.e., auto ERASE/WRITE) cycle.
After detection of a start condition the specified number
of clock cycles (respectively LOW to HIGH transitions
of CLK) must be provided. These clock cycles are
required to clock in all required opcode, address, and
data bits before an instruction is executed (see instruc-
tion set truth table). CLK and DI then become don't care
inputs waiting for a new start condition to be detected.
Note: CS must go LOW between consecutive
instructions.
3.3 Data In (DI)
Data In is used to clock in a START bit, opcode,
address, and data synchronously with the CLK input.
3.4 Data Out (DO)
Data Out is used in the READ and PRREAD mode to
output data synchronously with the CLK input (TPD
after the positive edge of CLK).
This pin also provides READY/BUSY status informa-
tion during ERASE and WRITE cycles. READY/BUSY
status information is available on the DO pin if CS is
brought HIGH after held LOW for minimum chip select
low time (TCSL) and an ERASE or WRITE operation
has been initiated.
The status signal is not available on DO, if CS is held
LOW or HIGH during the entire WRITE or ERASE
cycle. In all other cases DO is in the HIGH-Z mode. If
status is checked after the WRITE/ERASE cycle, a
pull-up resistor on DO is required to read the READY
signal.
3.5 Program Enable (PE)
This pin should be held HIGH in the programming
mode or when executing the Protect Register program-
ming instructions.
3.6 Protect Register Enable (PRE)
This pin should be held HIGH when executing all Pro-
tect Register instructions. Otherwise, it must be held
LOW for normal operations.
DS11181E-page 10
 2004 Microchip Technology Inc.