FOR AUTOMOTIVE 105

°C OPERATION 3-WIRE SERIAL E

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

11



Operation

All instructions are executed by inputting DI in synchronization with the rising edge of SK after CS goes high. An

instruction set is input in the order of start bit, instruction, address, and data.

low level is being input to CS, the S-93C46B/56B/66B is in standby mode, so the SK and DI inputs are invalid and no

instructions are allowed.



Start Bit

A start bit is recognized when the DI pin goes high at the rise of SK after CS goes high. After CS goes high, a start bit

is not recognized even if the SK pulse is input as long as the DI pin is low.

1. Dummy clock

SK clocks input while the DI pin is low before a start bit is input are called dummy clocks. Dummy clocks are

effective when aligning the number of instruction sets (clocks) sent by the CPU with those required for serial

memory operation. For example, when a CPU instruction set is 16 bits, the number of instruction set clocks can be

adjusted by inserting a 7-bit dummy clock for the S-93C46B and a 5-bit dummy clock for the S-93C56B/66B.

2. Start bit input failure

• When the output status of the DO pin is high during the verify period after a write operation, if a high level is input

to the DI pin at the rising edge of SK, the S-93C46B/56B/66B recognizes that a start bit has been input. To

prevent this failure, input a low level to the DI pin during the verify operation period (refer to “4.1 Verify

operation

”).

• When a 3-wire interface is configured by connecting the DI input pin and DO output pin, a period in which the

data output from the CPU and the serial memory collide may be generated, preventing successful input of the

start bit. Take the measures described in “ 3-Wire Interface (Direct Connection between DI and DO)”.