S-7750C Datasheet, PDF (22/44 Pages) Seiko Instruments Inc – PROGRAMMABLE PORT CONTROLLER (PORT EXPANDER WITH BUILT-IN E2PROM CIRCUIT)

PROGRAMMABLE PORT CONTROLLER (PORT EXPANDER WITH BUILT-IN E²PROM CIRCUIT)
S-7750C
Rev.1.1_00
6. 2 Write Protect
Write protect is available in the S-7750C. When the WP pin is connected to V_CCH, the Write operation in all memory
area is inhibited. When the WP pin is connected to GND, Write protect becomes invalid so that the Write operation in
all memory area is accepted.
Fix the WP pin during the period; from rising of SCL at installing the last bit (B0) in Write data until the completion of
Write period (max. 5 ms). Written data in the address is not assured if the condition of the WP pin is changed during
this period. Be sure to connect the WP pin to GND when you don’t use Write Protect. Write Protect is valid in the
range of power supply voltage.
t_WR
SCL
SDA
B0
Write Data
WP
Acknowledgment
signal
Stop
Condition
Period to fix WP pin
Start
Condition
Figure 27 Period to Fix WP Pin
6. 3 Acknowledgment polling
Acknowledge polling is used to find when the Write operation has completed. After receiving a stop condition the Write
operation has once started, all operations are inhibited to be performed so that the S-7750C cannot respond to the
signals transmitted from the master device. The master device sends a start condition, the device address and Read /
Write instruction code to the S-7750C (slave device), and detects the response from the slave device. It is possible to
find when the Write operation has completed. Thus if the slave device does not send an acknowledgment signal back,
the Write operation is in progress. If it sends an acknowledgment signal back, the Write operation has completed. Fix
the WP pin until an acknowledgment is confirmed. It is recommended to use the Read instruction “1” for the Read /
Write instruction code transmitted from the master device during acknowledgment polling.
6. 4 Irregular action
In the middle of inputting Write data, if inputting a stop condition in clock less than the specified data length (8-bit), the
S-7750C does not perform Write to the E²PROM. And it either does not perform Write to the E²PROM if receiving a
stop condition after receiving data over 9-bit. However, data in the register has been rewritten at the point when the
S-7750C has received the specified length data. Be sure not to input clock which exceeds the specified value due to
noise or other causes.
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Seiko Instruments Inc.