FT201X datasheet(39/49 Pages) ETC2

39 / 49 page

FT201X USB I2C SLAVE IC Datasheet

Version 1.3

Document No.: FT_000627 Clearance No.: FTDI# 264

10.5.4

Examples of Writing and Reading

When performing MTP memory write and read requests via the I2C protocol, users must first issue the

MTP address command along with 2 bytes representing the MTP memory address. The acknowledge

phase of this command represents the current status of the MTP memory (whether it is busy or not). If

the MTP memory is being accessed during an I2C access then the respective command and data phases

will NAK the master. The address will only be updated when the MTP memory is inactive.

Writing

The first part of the communication sets the address, and this is followed by the write command along

with the data to be written. The MTP memory write itself will be initiated when the FT201X receives an

MTP memory write command followed by a single data byte. The ACK phase represents the current

activity of the MTP memory (whether it is busy or not busy). A successful write will only occur when both

status phases acknowledge the master indicating that the MTP memory can start the write. Users wishing

to determine if the MTP memory write was successful should immediately try an MTP memory read to

verify the new contents.

This process of writing to the MTP memory is shown below:

Figure 10.2: Write EEPROM command sequence

Reading

In a similar way, the read is carried out as shown below.The first part of the communication sets the

address, and this is followed by the read command and a read cycle used to retrieve the data read back

from that address.

An MTP memory read will be initiated when the I2C slave receives an MTP read command. The

acknowledge during the command phase indicates whether or not the MTP memory will be able to service

the read request. If it is possible to carry out the read, the I2C moves into the data phase where it can

either continue with the read transaction until the slave successful returns an ACK along with the data or

if it receives NAK during the data phase it can abort the read transfer and try again.

Figure 10.3: Read EEPROM command sequence

0000000

0001_0000

S/Sr General call addr R/!W

MTP ADDR cmd

A/!A

Slave addr

R/!W

MTP ADR MSB

0000000

0001_0010

S/Sr General call addr R/!W

MTP WR cmd

A/!A

Slave addr

R/!W

MTP WR DATA

P/Sr

MTP Memory Address Phase

MTP memory Write Phase

MTP ADR LSB

0000000

0001_0000

S/Sr General call addr R/!W

MTP ADDR cmd

A/!A

Slave addr

R/!W

MTP ADR MSB

0000000

0001_0100

S/Sr General call addr R/!W

MTP WR cmd

A/!A

Slave addr

R/!W

MTP WR DATA

P/Sr

MTP ADR LSB

MTP Memory Address Phase

MTP memory Read Phase

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