S-34C02A Datasheet, PDF (14/34 Pages) Seiko Instruments Inc – 2-WIRE CMOS SERIAL E2PROM FOR DIMM SERIAL PRESENCE DETECT

2-WIRE CMOS SERIAL E²PROM FOR DIMM SERIAL PRESENCE DETECT
S-34C02A
Rev.1.2_00
6. 3 Hardware Write Protect
Write protect is available in the S-34C02A.
When the WP pin is connected to V_CC, the Write operation in all memory area is inhibited.
Fix the WP pin during the period from the start condition to the stop condition in the Write operation (Byte Write and
Page Write). Written data in the address is not assurable if the condition of the WP pin is changed during this
period. Refer to Figure 5 regarding the timing of Hardware Write Protect.
Be sure to connect the WP pin to GND when you don’t use Hardware Write Protect. Hardware Write Protect is valid
in the range of power supply voltage. If setting Hardware Write Protect valid, the S-34C02A does not generate an
acknowledgment signal.
In this case, the users cannot perform the SWP (Set RSWP), CWP (Clear RSWP), PSWP (Set PSWP) instructions.
6. 4 Software Write Protect
The S-34C02A has Permanent Software Write Protect (PSWP) and Reversible Software Write Protect (RSWP).
(1) PSWP
If the software protect has been set with the PSWP instruction, 50% of the lower address (addresses 00h to 7Fh)
in all memory is permanently Write-protected. This Write protect cannot be cleared by any instruction, or by
power-cycling the device, and regardless the state of WP pin. Also, once the PSWP instruction has been
successfully excuted, the S-34C02A no longer acknowledges any instruction (device code of “0110”) to access
the Write protect setting.
(2) RSWP
If the software protect has been set with the SWP (Set RSWP) instruction, 50% of the lower address (addresses
00h to 7Fh) in all memory is Write-protected. This write protect can be cleared with the CWP (Clear RSWP)
instruction.
These two instructions have the same format as a Byte Write instruction, but have a different device code. Like
the Byte Write instruction, it is followed by an address byte and a data byte, but in this case the contents can be
set in all “Don’t Care”. In the instructions of SWP and CWP, be sure to apply the high voltage of V_HV to the A0
pin, and input “H” or “L” to the A1 and A2 pins.
S
W
T
R
A
I
R
T
DEVICE
ADDRESS
T
E
WORD ADDRESS
S
T
O
DATA
P
SDA LINE
0 1 1 0 _{A2 A1 A0} 0
XXXXXXXX
XXXXXXXX
M
LRA
S
S/C
B
BW K
A
C
K
A
C
K
Figure 12 Software Write Protect
X : Don't care
Table 12 Device Select Code
Instruction
Memory Area Select ^*1
Set RSWP（SWP)
Clear RSWP（CWP)
Set PSWP（PSWP)^*1
Read SWP
Read CWP
Read PSWP^*1
Device code
B7 B6 B5 B4
1
0
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
Slave address
B3 B2 B1
A2 A1 A0
0
0
1
0
1
1
A2 A1 A0
0
0
1
0
1
1
A2 A1 A0
R/W
B0
R/W
0
0
0
1
1
1
Pin condition
A2 A1 A0
A2 A1 A0
V_SS V_SS V_HV
V_SS V_CC V_HV
A2 A1 A0
V_SS V_SS V_HV
V_SS V_CC V_HV
A2 A1 A0
*1. Slave addresses A2, A1, A0 are compared by the address input pins (A0, A1, A2) of a memory device with the address
value which is set beforehand.
14
Seiko Instruments Inc.