s-93c46b Seiko Instruments Inc., s-93c46b Datasheet - Page 22

• Manufacturer Part Number: s-93c46b
• Description: Cmos Serial E2prom
• Manufacturer: Seiko Instruments Inc.

22
CMOS SERIAL E
S-93C46B/56B/66B
3-Wire Interface (Direct Connection between DI and DO)
I/O Pins
1. Connection of input pins
2. Input and output pin equivalent circuits
There are two types of serial interface configurations: a 4-wire interface configured using the CS, SK, DI,
and DO pins, and a 3-wire interface that connects the DI input pin and DO output pin.
When the 3-wire interface is employed, a period in which the data output from the CPU and the data output
from the serial memory collide may occur, causing a malfunction. To prevent such a malfunction, connect
the DI and DO pins of the S-93C46B/56B/66B via a resistor (10 to 100 kΩ) so that the data output from the
CPU takes precedence in being input to the DI pin (refer to “ Figure 22 Connection of 3-Wire Interface ”).
All the input pins of the S-93C46B/56B/66B employ a CMOS structure, so design the equipment so that
high impedance will not be input while the S-93C46B/56B/66B is operating. Especially, deselect the CS
input (a low level) when turning on/off power and during standby. When the CS pin is deselected (a low
level), incorrect data writing will not occur. Connect the CS pin to GND via a resistor (10 to 100 kΩ pull-
down resistor). To prevent malfunction, it is recommended to use equivalent pull-down resistors for
pins other than the CS pin.
The following shows the equivalent circuits of input pins of the S-93C46B/56B/66B. None of the input
pins incorporate pull-up and pull-down elements, so special care must be taken when designing to
prevent a floating status.
Output pins are high-level/low-level/high-impedance tri-state outputs. The TEST pin is disconnected
from the internal circuit by a switching transistor during normal operation. As long as the absolute
maximum rating is satisfied, the TEST pin and internal circuit will never be connected.
2
PROM
Figure 22 Connection of 3-Wire Interface
CPU
SIO
Seiko Instruments Inc.
R: 10 to 100 kΩ
S-93C46B/56B/66B
DI
DO
Rev.4.3
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