TC664 datasheet(17/36 Pages) MICROCHIP

17 / 36 page

 2002 Microchip Technology Inc.

DS21737A-page 17

TC664/TC665

6.0

The TC664/TC665 devices contain 7 registers that pro-

vide a variety of data and functionality control to the

outside system. These registers are listed in Table 6-1.

Of key importance is the command byte information,

which is needed in the read and write protocols to

select the individual registers.

TABLE 6-1:

COMMAND BYTE ASSIGNMENTS

6.1

RPM-OUTPUT Register (RPM)

As discussed in Section 4.7, fan current pulses are

detected at the SENSE input of the TC664/TC665

device. The current pulse information is used to calcu-

late the fan RPM. The fan RPM data is then written to

the RPM register. RPM is a 9-bit register that provides

the RPM information in 50 RPM (8-bit) or 25 RPM (9-

bit) increments. This is selected via RES (bit 6<0>) in

the Configuration Register, with ‘0’ = 50 RPM and

‘1’ = 25 RPM. The default state is zero (50 RPM). The

maximum fan RPM value that can be read is

12775 RPM. If this value is exceeded, RCO (bit 3<0>)

in the Status Register will be set to a '1' to indicate that

a counter overflow of the RPM Register has occurred.

mat.

RPM OUTPUT REGISTER (RPM)

Command

Read

Write

POR Default State

Function

RPM

0000 0000

X—

0 0000 0000

RPM Output

FAN_FAULT

0000 0010

0000 1010

Fan Fault Threshold

CONFIG

0000 0100

0000 1010

Configuration

STATUS

0000 0101

X—

00X0 0X00

Status. See Section 6.4, Status

DUTY_CYCLE

0000 0110

0000 0010

Fan Speed Duty Cycle

MFR_ID

0000 0111

X—

0101 0100

Manufacturer Identification

VER_ID

0000 1000

X—

0000 00XX

Version Identification:

(XX = ‘10’ TC664, XX = ‘11’ TC665)

D(8)

D(7)

D(6)

D(5)

D(4)

D(3)

D(2)

D(1)

D(0)

RPM

0000000000

000000001

000000010

.........

111111110

12750

111111111

12775

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