S-93C76A-H Datasheet, PDF (13/28 Pages) Seiko Instruments Inc – FOR AUTOMOTIVE OPERATION 3-WIRE SERIAL E2PROM

Rev.3.1_01
FOR AUTOMOTIVE 105°C OPERATION 3-WIRE SERIAL E²PROM
S-93C76A H Series
3. Write enable (EWEN) and write disable (EWDS)
The EWEN instruction is used to enable a write operation. The status in which a write operation is enabled is
called the program-enabled mode.
The EWDS instruction is used to disable a write operation. The status in which a write operation is disabled is
called the program-disabled mode.
The write operation is disabled upon power application and detection of a low supply voltage. To prevent an
unexpected write operation due to external noise or a CPU malfunctions, it should be kept in write disable mode
except when performing write operations, after power-on and before shutdown.
CS
Standby
SK
1 2 3 4 5 6 7 8 9 10 11 12 13
DI
<1> 0 0
11 = EWEN
8Xs
00 = EWDS
Figure 11 Write Enable/Disable Timing
 Start Bit
A start bit is recognized by latching the high level of DI at the rising edge of SK after changing CS to high (start bit
recognition). A write operation begins by inputting the write instruction and setting CS to low. Subsequently, by setting
CS to high again, the DO pin outputs a low level if the write operation is still in progress and a high level if the write
operation is complete (verify operation). Therefore, only after a write operation, in order to input the next command, CS
is set to high, which switches the DO pin from a high-impedance state (High-Z) to a data output state. However, if start
bit is recognized, the DO pin returns to the high-impedance state (refer to Figure 5 Timing Chart).
Make sure that data output from the CPU does not interfere with the data output from the serial memory IC when
configuring a 3 -wire interface by connecting the DI input pin and DO output pin, as such interference may cause a start
bit fetch problem. Take the measures described in “ 3-Wire Interface (Direct Connection between DI and DO)”.
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