AMC80

SBOS559

– MAY 2011

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enable or disable the hardware interrupts. Additional digital inputs are provided for daisy-chaining the interrupt

output pin, INT. This configuration is achieved by connecting multiple external temperature sensors (for example,

the TMP75) to the board temperature interrupt (BTI) input and/or the GPI/CI input. The chassis intrusion (CI)

input is designed to accept an active high signal from an external circuit that latches (for example, when the

chassis from a server rack is removed).

INTERFACE AND CONTROL

The SMBus control lines in the AMC80 include SDA, SCL, and the A0 to A2 address pins, which allow up to

eight AMC80 devices to be on the same bus. The AMC80 can only operate as a slave device. The SCL line

controls only the serial interface; all other clock-related functions within the AMC80 (such as the ADC and fan

counters) operate with a separate asynchronous internal clock. The default power-on SMBus address for the

AMC80 is '0101'(A2)(A1)(A0) binary, where (A2)(A1)(A0) is the SMBus address.

When using the SMBus interface, a write command always consists of the AMC80 SMBus interface address

byte, followed by the internal address register byte, and then the data byte (see Figure 8).

See Figure 9 for the read operation timing. There are two cases for a read operation:

1. If the contents of the Internal Address Register are known, simply read the AMC80 with the SMBus interface

address byte, followed by the data byte read from the ADC80.

2. If the internal Address Register contents are unknown, write to the AMC80 with the SMBus interface address

byte, followed by the internal address register bye. Then restart the serial communication with a read that

consist of the SMBus interface address byte, followed by the data byte read from the AMC80.

Table 1. Register Overview

INTERNAL

POWER-ON

ADDRESS

VALUE

REGISTER

(HEX)

(HEX)

NOTES

Configuration Register

00

08

Interrupt Status Register 1

01

xx

Indeterminate

Interrupt Status Register 2

02

xx

Indeterminate

Interrupt Mask Register 1

03

00

Interrupt Mask Register 2

04

00

Fan Divisor/RST_OUT/OS Register

05

14

FAN1 and FAN2 divisor = 2 (count of 153 = 4400 RPM)

OS Configuration/Temperature Resolution

06

x1

Four MSBs are indeterminate

Register

Conversion Rate Register

07

40

Voltage/Temperature Channel Disable

08

00

Allows voltage monitoring inputs to be disabled

Register

Input Mode Register

09

00

ADC Control Register

0A

02

Conversion Rate Count Register

0B

40

Value RAM Register

20 to 29

xx

Indeterminate

Value RAM Register

2A to 3D

xx

Indeterminate

Value RAM Register

3E

80

Value RAM Register

3F

09

10

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© 2011, Texas Instruments Incorporated

Product Folder Link(s): AMC80