MCP79400 datasheet(20/42 Pages) MICROCHIP

20 / 42 page

MCP7940X

DS25009C-page 20

 2011 Microchip Technology Inc.

6.2

6.2.1

ID BYTE WRITE

Following the Start condition from the master, the

control code and the R/W bit (which is a logic low) are

clocked onto the bus by the master transmitter. This

indicates to the addressed slave receiver that a byte

with a word address will follow after it has generated an

Acknowledge bit during the ninth clock cycle.

Therefore, the next byte transmitted by the master is

the word address and will be written into the Address

Pointer of the MCP7940X. After receiving another

Acknowledge signal from the MCP7940X, the master

device transmits the data word to be written into the

addressed

memory

location.

The

MCP7940X

acknowledges again and the master generates a Stop

condition. This initiates the internal write cycle, and,

during this time, the MCP7940X does not generate

Acknowledge signals for Unique ID Write commands. If

an attempt is made to write to an address and the

protection is set then the device will acknowledge the

command but no write cycle will occur, no data will be

written, and the device will immediately accept a new

command. After a Byte Write command, the internal

address counter will point to the address location

following the one that was just written.

Note:

Addressing undefined ID locations will

result in the MCP7940X not acknowledg-

ing the address.

MCP79400 Datasheet(PDF) 20 Page - Microchip Technology