TC665 Microchip Technology Inc., TC665 Datasheet - Page 17

• Manufacturer Part Number: TC665
• Description: Smbus Pwm Fan Speed Controllers With Fan Fault Detection
• Manufacturer: Microchip Technology Inc.

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.
TABLE 6-1:
6.1
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
REGISTER 6-1:
RPM
FAN_FAULT
CONFIG
STATUS
DUTY_CYCLE
MFR_ID
VER_ID
2002 Microchip Technology Inc.
D(8)
0
0
0
1
1
Register
.
.
REGISTER SET
RPM-OUTPUT Register (RPM)
D(7)
0
0
0
1
1
.
.
COMMAND BYTE ASSIGNMENTS
Command
0000 0000
0000 0010
0000 0100
0000 0101
0000 0110
0000 0111
0000 1000
RPM OUTPUT REGISTER (RPM)
D(6)
0
0
0
1
1
.
.
Read
D(5)
0
0
0
1
1
X
X
X
X
X
X
X
.
.
Write
D(4)
—
—
—
—
X
X
X
0
0
0
1
1
.
.
POR Default State
0 0000 0000
D(3)
Of key importance is the command byte information,
which is needed in the read and write protocols to
select the individual registers.
0000 1010
0000 1010
00X0 0X00
0000 0010
0101 0100
0000 00XX
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.
Register 6-1 shows the RPM output register 9-bit for-
mat.
0
0
0
1
1
.
.
D(2)
0
0
0
1
1
.
.
RPM Output
Fan Fault Threshold
Configuration
Status. See Section 6.4, Status
Register explanation of X
Fan Speed Duty Cycle
Manufacturer Identification
Version Identification:
(XX = ‘10’ TC664, XX = ‘11’ TC665)
TC664/TC665
D(1)
0
0
1
1
1
.
.
Function
D(0)
0
1
0
0
1
.
.
DS21737A-page 17
12750
12775
RPM
25
50
0