Philips Semiconductors

Product data sheet

SA56004X

±1 °C accurate, SMBus-compatible, 8-pin, remote/local

digital temperature sensor with over temperature alarms

2004 Oct 06

14

Programmable offset register (remote only)

Table 12. Remote Temperature Offset registers

(RTOHB and RTOLB)

High Byte (Read/Write address 11h)

Bit

D7

D6

D5

D4

D3

D2

D1

D0

Value

Sign

64

32

16

8

4

2

1

POR default RTOHB = RTOLB = 00h.

Low Byte (Read/Write address 12h)

Bit

D7

D6

D5

D4

D3

D2

D1

D0

Value

0.5

0.25

0.125

0

0

0

0

0

POR default RTOLB = 00h.

ALERT mode register

Table 13. ALERT mode register (AM)

(Read and Write address BFh)

Bit

D7

D6

D5

D4

D3

D2

D1

D0

Value

0

0

0

0

0

0

0

ALERT mode

D7-D1: is not defined and defaults to ‘0’.

D0: The ALERT output is in Interrupt mode when this bit is LOW.

The ALERT output is in comparator mode when this bit is HIGH.

Other registers

The Manufacturers ID register has a default value A1h (1010 0001)

and a read address FEh.

The Die Revision Code register has a default value 00h

(0000 0000) and read address FFh. This register will increment by 1

every time there is a revision to the die.

One-shot register

The one-shot register is used to initiate a single conversion and

comparison cycle when the device is in the standby mode; upon

completion of the single conversion cycle the device returns to the

standby mode. It is not a data register; it is the write operation that

causes the one-shot conversion. The data written to this register is

not stored; a FF value will always be read from this register. To

initiate an one-shot operation, send a standard write command with

the command byte of 0Fh (One-Shot Write Address).

INTERRUPTION LOGIC

FUNCTIONAL DESCRIPTION

ALERT output

The ALERT output is used to signal Alert interruptions from the

device to the SMBus or other system interrupt handler and it is

active LOW. Because this is an open drain output, a pull-up resistor

(typically 10 k

a common interrupt line on the same SMBus.

The ALERT function is very versatile and accommodates three

separate operating modes: 1) a temperature comparator, 2) a

system interrupt based on temperature, and 3) an SMBus Alert

Response Address (ARA) response. The ARA and interrupt modes

are different only in how the user interacts with the SA56004X.

At the end of every temperature reading, digital comparators

determine if the readings are above the HIGH or T_CRIT setpoint or

below the LOW setpoint register values. If so, the corresponding bit

in the Status register is set. If the ALERT mask bit 7 of the

Configuration register is not HIGH, then, any bit set in the Status

register, other than the BUSY (D7) and OPEN (D2), will cause the

ALERT output pin to be active-LOW. An alert will be triggered after

any conversion cycle that finds the temperature is out of the limits

defined by the setpoint registers. In order to trigger an ALERT in all

alert modes, the ALERT mask bit 7 of the Configuration register

must be cleared (not HIGH).

ALERT output in Comparator Mode

When operating the SA56004X in a system that utilizes a SMBus

controller not having an interrupt, the ALERT output may be

operated as a temperature comparator. In this mode, when the

condition that triggered the ALERT to be asserted is no longer

present, the ALERT output is released as it goes HIGH. In order to

use the ALERT output as a temperature comparator, bit D0, the

ALERT configure bit, in the ALERT Mode (AM) register must be set

HIGH. This is not the POR default.

ALERT output in Interrupt Mode

In the interrupt mode, the ALERT output is used to provide an

interrupt signal that remains asserted until the interrupt service

routine has elapsed. In the interrupt operating mode, a read of the

Status register will set the ALERT mask bit 7 of the Configuration

register if any of the temperature alarm bits of the status register is

set with exception of BUSY (D7) and OPEN (D2). This protocol

prevents further ALERT output triggering until the master device has

reset the ALERT mask bit at the end of the interrupt service routine.

The Status register bits are cleared only upon a read of the status

register by the serial bus master (See Figure 13). In order for the

ALERT output to be used as an interrupt, the ALERT Configure bit

D0 of the ALERT Mode (AM) register must be set LOW. Note, this is

the POR default.

Remote Temp

High Limit

SA56004–X

Status Register

Bit 4(RHIGH)

Remote

Diode Temp

A

B,C

D

ALERT pin

SR02502

E, F

Figure 13. ALERT output in Interrupt Mode

The following events summarizes the ALERT output interrupt mode

of operation:

Event A: Master senses ALERT output being active-LOW.

Event B: Master reads the SA56004X Status register to determine

what cause the ALERT interrupt.

Event C: SA56004X clears the Status register, resets the ALERT

output HIGH, and sets the ALERT mask bit 7 in the Configuration

register.

Event D: A new conversion result indicates the temperature is still

above the high limit, however the ALERT pin is not activated due to

the ALERT mask.