TC655 Microchip Technology Inc., TC655 Datasheet - Page 17

• Manufacturer Part Number: TC655
• Description: Dual Smbus Pwm Fan Speed Controllers With Fan Fault Detection
• Manufacturer: Microchip Technology Inc.

6.0
The TC654/TC655 devices contain 9 registers that pro-
vide a variety of data and functionality control to the
outside system. These registers are listed below in
TABLE 6-1:
6.1
As discussed in Section 4.7, fan current pulses are
detected at the SENSE1 and SENSE2 inputs of the
TC654/TC655 device. The current pulse information is
used to calculate the fan RPM. The fan RPM data for
fans 1 & 2 is then written to registers RPM1 and RPM2,
respectively. RPM1 and RPM2 are 9-bit registers that
provide the RPM information in 50 RPM (8-bit) or
REGISTER 6-1:
RPM1
RPM2
FAN_FAULT1
FAN_FAULT2
CONFIG
STATUS
DUTY_CYCLE
MFR_ID
VER_ID
2002 Microchip Technology Inc.
D(8)
0
0
0
1
1
Register
.
.
REGISTER SET
RPM-OUTPUT1 & RPM-OUTPUT2
Registers (RPM1 & RPM2)
D(7)
0
0
0
1
1
.
.
COMMAND BYTE ASSIGNMENTS
Command
0000 0000
0000 0001
0000 0010
0000 0011
0000 0100
0000 0101
0000 0110
0000 0111
0000 1000
RPM OUTPUT REGISTERS (RPM1 & RPM2)
D(6)
0
0
0
1
1
.
.
Read
D(5)
0
0
0
1
1
X
X
X
X
X
X
X
X
X
.
.
Write
D(4)
—
—
—
—
—
X
X
X
X
0
0
0
1
1
.
.
POR Default State
0 0000 0000
0 0000 0000
D(3)
Table 6-1. Of key importance is the command byte
information, which is needed in the read and write pro-
tocols in order to select the individual registers.
0000 1010
0000 1010
0000 1010
00X0 0X00
0000 0010
0101 0100
0000 000X
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, R2CO (bit 4<0>)
and R1CO (bit 3<0>) in the Status Register will be set
to a '1' to indicate that a counter overflow of the respec-
tive RPM register has occurred. Register 6-1 shows the
RPM output register 9-bit format.
0
0
0
1
1
.
.
D(2)
0
0
0
1
1
.
.
RPM Output 1
RPM Output 2
Fan Fault 1 Threshold
Fan Fault 2 Threshold
Configuration
Status. See Section 6.4, Status
Register explanation of X
Fan Speed Duty Cycle
Manufacturer Identification
Version Identification:
(X = ‘0’ TC654, X = ‘1’ TC655)
TC654/TC655
D(1)
0
0
1
1
1
.
.
Function
D(0)
0
1
0
0
1
.
.
DS21734A-page 17
12750
12775
RPM
25
50
0