3-WIRE SERIAL E
2
PROM
Rev.7.0
_00
S-93C76A
Seiko Instruments Inc.
11
2. Writing (WRITE, ERASE, WRAL, ERAL)
Write instructions (WRITE, ERASE, WRAL, and ERAL) are used to start writing data to the non-volatile memory by
making CS “L” after the specified number of clocks has been input.
The write operation is completed within the write time t
PR
(10 ms) no matter which write instruction is used. The
typical write time is less than half 10 ms. If the end of the write operation is known, therefore, the write cycle can
be minimized. To ascertain the end of a write operation, make CS “L” to start the write operation and then make
CS “H” again to check the status of the DO output pin. This series of operations is called a verify operation.
If DO outputs “L” during the verify operation period in which CS is “H”, it indicates that a write operation is in
progress. If DO outputs “H”, it indicates that the write operation is finished. The verify operation can be executed
as many times as required. This operation can be executed in two ways. One is detecting the positive transition
of DO output from “L” to “H” while holding CS at “H”. The other is detecting the positive transition of DO output
from “L” to “H” by making CS “H” once and checking DO output, and then returning CS to “L”.
During the write period, SK and DI are invalid. Do not input any instructions during this period. Input an
instruction while the DO pin is outputting “H” or is in a high-impedance state. Even while the DO pin is outputing
“H”, DO immediately goes into a high-impedance (High-Z) state if “H” of DI (start bit) is input at the rising edge of
SK.
Keep DI “L” during the verify operation period.
2. 1 Writing data (WRITE)
This instruction is used to write 16-bit data to a specified address.
After making CS “H”, input a start bit, the WRITE instruction, an address, and 16-bit data. If data of more than
16 bits is input, the written data is sequentially shifted at each clock, and the 16 bits input last are the valid
data. The write operation is started when CS is made “L”. It is not necessary to set data to “1” before it is
written.
DO
<1>
2 3
4
5
6
7 8 9 10 11 12 13 14 29
0 1 X A8 A7 A6 A5 A4 A3 A2 A1 A0 D15 D0
DI
SK
CS
High-Z
t
CDS
t
SV
t
PR
usy
ead
Standby
High-Z
t
HZ1
Verify
1
Figure 7 Data Write Timing
2. 2 Erasing data (ERASE)
This instruction is used to erase specified 16-bit data. All the 16 bits of the data are “1”. After making CS
“H”, input a start bit, the ERASE instruction, and an address. It is not necessary to input data. The data
erase operation is started when CS is made “L”.
DO
<1>
2 3
4
5
6
7 8 9 10 11 12 13
1 1 X A8 A7 A6 A5 A4 A3 A2 A1 A0
DI
SK
CS
High-Z
t
CDS
t
SV
t
PR
usy
ead
Standby
High-Z
t
HZ1
Verify
1
Figure 8 Data Erase Timing
