EVAL-ADM1026EB datasheet(16/56 Pages) AD

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ADM1026

Rev. A | Page 16 of 56

Block Read

In this 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 case of the ADM1026 this is done by a

send byte operation to set a RAM address, or by a write

byte/word operation to set an EEPROM address. The block read

operation 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:

The master device asserts a start condition on the SDA.

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

write bit (low).

The addressed slave device asserts an ACK on the SDA.

The master sends a command code that tells the slave

device to expect a block read. The ADM1026 command

code for a block read is A1h (10100001).

The slave asserts an ACK on the SDA.

The master asserts a repeat start condition on the SDA.

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

read bit (high).

The slave asserts an ACK on the SDA.

The ADM1026 sends a byte count data byte that tells the

master how many data bytes to expect. The ADM1026

always returns 32 data bytes (20h), the maximum allowed

by the SMBus 1.1 specification.

10. The master asserts an ACK on the SDA.

11. The master receives 32 data bytes.

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

13. The ADM1026 issues a PEC byte to the master. The master

should check the PEC byte and issue 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 the SDA to end the

transaction.

SLAVE

ADDRESS

COMMAND

A1h BLOCK

READ

DATA

PEC

BYTE

COUNT

A DATA 1 A

SLAVE

ADDRESS

Figure 26. Block Read from EEPROM or RAM

When block reading from EEPROM, Bit 0 of EEPROM

Note that although the ADM1026 supports packet error

checking (PEC), its use is optional. The PEC byte is calculated

using CRC-8. The frame check sequence (FCS) conforms to

CRC-8 by the polynomial:

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

Consult the SMBus 1.1 Specification for more information.

MEASUREMENT INPUTS

The ADM1026 has 17 external analog measurement pins that

can be configured to perform various functions. It also meas-

ures two supply voltages, 3.3 V MAIN and 3.3 V STBY, and the

internal chip temperature.

Pins 25 and 26 are dedicated to remote temperature measure-

ment, while Pins 27 and 28 can be configured as analog inputs

with a range of 0 V to 2.5 V, or as inputs for a second remote

temperature sensor.

Pins 29 to 33 are dedicated to measuring VBAT, +5 V, −12 V,

+12 V supplies, and the processor core voltage VCCP. The

remaining analog inputs, Pins 34 to 41, are general-purpose

analog inputs with a range of 0 V to 2.5 V (Pins 34 and 35) or

0 V to 3 V (Pins 36 to 41).

A-to-D Converter (ADC)

These inputs are multiplexed into the on-chip, successive

approximation, analog-to-digital converter. The ADC has a

resolution of 8 bits. The basic input range is 0 V to 2.5 V, which

is the input range of AIN6 to AIN9, but five of the inputs have

built-in attenuators to allow measurement of VBAT, +5 V, −12 V,

+12 V, and the processor core voltage VCCP, without any external

components. To allow the tolerance of these supply voltages, the

ADC produces an output of 3/4 full scale (decimal 192) for the

nominal input voltage, and so has adequate headroom to cope

with over voltages. Table 6 shows the input ranges of the analog

inputs and output codes of the ADC.

When the ADC is running, it samples and converts an analog

or local temperature input every 711 µs (typical value). Each

input is measured 16 times and the measurements are averaged

to reduce noise, so the total conversion time for each input is

11.38 ms.

Measurements on the remote temperature (D1 and D2) inputs

take 2.13 ms. These are also measured 16 times and are

averaged, so the total conversion time for a remote temperature

input is 34.13 ms.

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