FOR AUTOMOTIVE 105

°C OPERATION 3-WIRE SERIAL E

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

Seiko Instruments Inc.

13

4. Writing (WRITE, ERASE, WRAL, ERAL)

A write operation includes four write instructions: data write (WRITE), data erase (ERASE), chip write (WRAL), and

chip erase (ERAL).

A write instruction (WRITE, ERASE, WRAL, ERAL) starts a write operation to the memory cell when a low level is

input to CS after a specified number of clocks have been input. The SK and DI inputs are invalid during the write

period, so do not input an instruction.

Input an instruction while the output status of the DO pin is high or high impedance (High-Z).

A write operation is valid only in program enable mode (refer to “5. Write enable (EWEN) and write disable

(EWDS)

”).

4. 1 Verify operation

completion of the write operation is recognized, the write cycle can be minimized. A sequential operation to

confirm the status of a write operation is called a verify operation.

(1) Operation

After the write operation has started (CS = low), the status of the write operation can be verified by

confirming the output status of the DO pin by inputting a high level to CS again. This sequence is called a

verify operation, and the period that a high level is input to the CS pin after the write operation has started

is called the verify operation period.

The relationship between the output status of the DO pin and the write operation during the verify

operation period is as follows.

• DO pin = low: Writing in progress (busy)

• DO pin = high: Writing completed (ready)

(2) Operation example

There are two methods to perform a verify operation: Waiting for a change in the output status of the DO

pin while keeping CS high, or suspending the verify operation (CS = low) once and then performing it again

to verify the output status of the DO pin. The latter method allows the CPU to perform other processing

during the wait period, allowing an efficient system to be designed.

Caution 1. Input a low level to the DI pin during a verify operation.

2. If a high level is input to the DI pin at the rise of SK when the output status of the DO pin is high,

the S-93C46B/56B/66B latches the instruction assuming that a start bit has been input. In this

case, note that the DO pin immediately enters a high-impedance

(High-Z) state.