ADM1069ACPZ datasheet(30/32 Pages) AD

30 / 32 page

ADM1069

Rev. C | Page 30 of 32

The ADM1069 sends a byte-count data byte that tells the

master how many data bytes to expect. The ADM1069

always returns 32 data bytes (0x20), which is the maximum

allowed by the SMBus Version 1.1 specification.

READ OPERATIONS

The ADM1069 uses the following SMBus read protocols.

Receive Byte

10. The master asserts an ACK on SDA.

In a receive byte operation, the master device receives a single

byte from a slave device, as follows:

11. The master receives 32 data bytes.

12. The master asserts an ACK on SDA after each data byte.

The master device asserts a start condition on SDA.

13. The master asserts a stop condition on SDA to end the

transaction.

The master sends the 7-bit slave address followed by the

read bit (high).

The addressed slave device asserts an ACK on SDA.

SLAVE

ADDRESS

SW A

COMMAND 0xFD

(BLOCK READ)

SLAVE

ADDRESS

BYTE

COUNT

910

DATA

The master receives a data byte.

The master asserts a NACK on SDA.

The master asserts a stop condition on SDA, and the

transaction ends.

In the ADM1069, the receive byte protocol is used to read a

single byte of data from a RAM or EEPROM location whose

address has previously been set by a send byte or write byte/

word operation, as shown in Figure 45.

Figure 46. Block Read from the EEPROM or RAM

Error Correction

The ADM1069 provides the option of issuing a packet error

correction (PEC) byte after a write to the RAM, a write to the

EEPROM, a block write to the RAM/EEPROM, or a block read

from the RAM/ EEPROM. This option enables the user to verify

that the data received by or sent from the ADM1069 is correct.

The PEC byte is an optional byte sent after the last data byte has

been written to or read from the ADM1069. The protocol is the

same as a block read for Step 1 to Step 12 and then proceeds as

follows:

SLAVE

ADDRESS

DATA

Figure 45. Single Byte Read from the EEPROM or RAM

Block Read

In a block read operation, the master device reads a block of

data from a slave device. The start address for a block read must

have been set previously. In the ADM1069, this is done by a

send byte operation to set a RAM address, or a write byte/word

operation to set an EEPROM address. The block read operation

itself consists of a send byte operation that sends a block read

command to the slave, immediately followed by a repeated start

and a read operation that reads out multiple data bytes, as

follows:

13. The ADM1069 issues a PEC byte to the master. The master

checks the PEC byte and issues another block read, if the

PEC byte is incorrect.

14. A NACK is generated after the PEC byte to signal the end

of the read.

15. The master asserts a stop condition on SDA to end the

transaction.

The master device asserts a start condition on SDA.

The master sends the 7-bit slave address followed by the

write bit (low).

Note that the PEC byte is calculated using CRC-8. The frame

check sequence (FCS) conforms to CRC-8 by the polynomial

The addressed slave device asserts an ACK on SDA.

C(x) = x8 + x2 + x1 + 1

The master sends a command code that tells the slave

device to expect a block read. The ADM1069 command

code for a block read is 0xFD (1111 1101).

See the SMBus Version 1.1 specification for details.

An example of a block read with the optional PEC byte is shown

in Figure 47.

The slave asserts an ACK on SDA.

The master asserts a repeat start condition on SDA.

SLAVE

ADDRESS

SW A

COMMAND 0xFD

(BLOCK READ)

SLAVE

ADDRESS

BYTE

COUNT

910

DATA

PEC

The master sends the 7-bit slave address followed by the

read bit (high).

The slave asserts an ACK on SDA.

Figure 47. Block Read from the EEPROM or RAM with PEC

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