M93C86 datasheet(14/37 Pages) STMICROELECTRONICS

14 / 37 page

Instructions

M93C86, M93C76, M93C66, M93C56, M93C46

14/37

Doc ID 4997 Rev 10

5.1

Read Data from Memory

The Read Data from Memory (READ) instruction outputs data on Serial Data Output (Q).

When the instruction is received, the op-code and address are decoded, and the data from

the memory is transferred to an output shift register. A dummy 0 bit is output first, followed

by the 8-bit byte or 16-bit word, with the most significant bit first. Output data changes are

triggered by the rising edge of Serial Clock (C). The M93Cx6 automatically increments the

internal address register and clocks out the next byte (or word) as long as the Chip Select

Input (S) is held High. In this case, the dummy 0 bit is not output between bytes (or words)

and a continuous stream of data can be read.

5.2

Write Enable and Write Disable

The Write Enable (WEN) instruction enables the future execution of erase or write

instructions, and the Write Disable (WDS) instruction disables it. When power is first

applied, the M93Cx6 initializes itself so that erase and write instructions are disabled. After

an Write Enable (WEN) instruction has been executed, erasing and writing remains enabled

until an Write Disable (WDS) instruction is executed, or until VCC falls below the power-on

reset threshold voltage. To protect the memory contents from accidental corruption, it is

advisable to issue the Write Disable (WDS) instruction after every write cycle. The Read

Data from Memory (READ) instruction is not affected by the Write Enable (WEN) or Write

Disable (WDS) instructions.

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