USB2513 datasheet(34/57 Pages) MICROCHIP

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USB251xB/xBi

DS00001692D-page 34

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5.3.2.1

Block Write/Read

The block write begins with a slave address and a write condition. After the command code, the host issues a byte count

which describes how many more bytes will follow in the message. If a slave had 20 bytes to send, the first byte would

be the number 20 (14h), followed by the 20 bytes of data. The byte count may not be zero. A block write or read allows

a transfer maximum of 32 data bytes.

TABLE 5-2:

BLOCK WRITE

5.3.2.2

Block Read

A block read differs from a block write in that the repeated start condition exists to satisfy the I2C specification’s require-

ment for a change in the transfer direction.

TABLE 5-3:

BLOCK READ

5.3.2.3

Invalid Protocol Response Behavior

Note that any attempt to update registers with an invalid protocol will not be updated. The only valid protocols are write

block and read block (described above), where the hub only responds to the 7-bit hardware selected slave address

(0101100b). Also, the only valid registers for the hub are outlined in Section 5.1 on page 19. Attempts to access any

other registers will return no response.

5.3.3

SLAVE DEVICE TIMEOUT

Devices in a transfer can abort the transfer in progress and release the bus when any single clock low interval exceeds

25 ms (TTIMEOUT, MIN). The master must detect this condition and generate a stop condition within or after the transfer

of the interrupted data byte. Slave devices must reset their communication and be able to receive a new START condi-

tion no later than 35 ms (TTIMEOUT, MAX).

Note:

For the following SMBus tables:

Note:

Some simple devices do not contain a clock low drive circuit; this simple kind of device typically resets its

communications port after a start or stop condition. The slave device timeout must be implemented.

Denotes Master-to-Slave

Denotes Slave-to-Master

Slave Address

171

...

Byte Count = N

Data byte 1

Data byte 2

Data byte N

Slave Address

...

Byte Count = N

Data byte 2

Data byte 1

Data byte N

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