93C66A Datasheet, PDF (3/12 Pages) Microchip Technology – 4K 5.0V Automotive Temperature Microwire Serial EEPROM

93C66A/B
2.0 PIN DESCRIPTION
2.1 Chip Select (CS)
A high level selects the device; a low level deselects the
device and forces it into standby mode. However, a pro-
gramming cycle which is already in progress will be
completed, regardless of the Chip Select (CS) input
signal. If CS is brought low during a program cycle, the
device will go into standby mode as soon as the pro-
gramming cycle is completed.
CS must be low for 250 ns minimum (TCSL) between
consecutive instructions. If CS is low, the internal con-
trol logic is held in a RESET status.
2.2 Serial Clock (CLK)
The Serial Clock (CLK) is used to synchronize the com-
munication between a master device and
the 93C66A/B. Opcodes, addresses, 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 continued
anytime with respect to clock high time (TCKH) 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 the 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 a START condition).
CLK cycles are not required during the self-timed
WRITE (i.e., auto ERASE/WRITE) cycle.
After detecting a START condition, the specified num-
ber of clock cycles (respectively low to high transitions
of CLK) must be provided. These clock cycles are
required to clock in all required opcodes, addresses,
and data bits before an instruction is executed
(Table 2-1 and Table 2-2). 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.
2.3 Data In (DI)
Data In (DI) is used to clock in a START bit, opcode,
address, and data synchronously with the CLK input.
2.4 Data Out (DO)
Data Out (DO) is used in the READ 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 being 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 during the entire ERASE or
WRITE cycle. In this case, DO is in the HIGH-Z mode.
If status is checked after the ERASE/WRITE cycle, the
data line will be high to indicate the device is ready.
TABLE 2-1: INSTRUCTION SET FOR 93C66A
Instruction SB Opcode
Address
Data In Data Out Req. CLK Cycles
ERASE
1
11
A8 A7 A6 A5 A4 A3 A2 A1 A0
—
(RDY/BSY)
12
ERAL
1
00
1 0XXXXXXX
—
(RDY/BSY)
12
EWDS
1
00
0 0XXXXXXX
—
HIGH-Z
12
EWEN
1
00
1 1XXXXXXX
—
HIGH-Z
12
READ
1
10
A8 A7 A6 A5 A4 A3 A2 A1 A0
—
D7 - D0
20
WRITE
1
01
A8 A7 A6 A5 A4 A3 A2 A1 A0 D7 - D0 (RDY/BSY)
20
WRAL
1
00
0 1 X X X X X X X D7 - D0 (RDY/BSY)
20
TABLE 2-2: INSTRUCTION SET FOR 93C66B
Instruction SB Opcode
Address
Data In
ERASE
1
ERAL
1
EWEN
1
EWDS
1
READ
1
WRITE
1
WRAL
1
11
A7 A6 A5 A4 A3 A2 A1 A0
—
00
1 0XXXXXX
—
00
1 1XXXXXX
—
00
0 0XXXXXX
—
10
A7 A6 A5 A4 A3 A2 A1 A0
—
01
A7 A6 A5 A4 A3 A2 A1 A0 D15 - D0
00
0 1 X X X X X X D15 - D0
Data Out
(RDY/BSY)
(RDY/BSY)
HIGH-Z
HIGH-Z
D15 - D0
(RDY/BSY)
(RDY/BSY)
Req. CLK Cycles
11
11
11
11
27
27
27
© 1998 Microchip Technology Inc.
Preliminary
DS21207B-page 3