FOR AUTOMOTIVE 105

°C OPERATION 3-WIRE SERIAL E

S-93C46B/56B/66B H Series

Seiko Instruments Inc.

21



3-Wire Interface (Direct Connection between DI and DO)

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 k

input to the DI pin (refer to “Figure 20 Connection of 3-Wire Interface”).

CPU

DI

SIO

DO

S-93C46B/56B/66B

R : 10 to 100 k

Ω

Figure 20 Connection of 3-Wire Interface



I/O Pin

1. Connection of input pins

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 k

malfunction, it is recommended to use equivalent pull-down resistors for pins other than the CS pin.

2. Equivalent circuit of input and output 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.