SSC050-01 Datasheet, PDF (47/79 Pages) Maxim Integrated Products – Two-Wire Serial Backplane Controller

Control Registers
Control Register Definition
SSC050-01
Data Sheet
3Ah: Fan Speed Current Count 2 (FSCC2)
Register Name:
Address:
Reset Value:
Description
FSCC2
3Ah
0000_0000b
Fan Speed Current Count 2.
This register affects pin P2.6.
7
6
5
4
3
2
1
0
Fan Speed Current Count
Bit(s) Bit Label
7 FSCO7-0
Access Description
R/W These eight bits, when enabled by setting the FSCEN bit in the FSC2 register pro-
vide the user with an accurate binary fan speed count value which can be used to
determine the current RPM value of the fan. A minimum of one complete revolution
of the fan is required to generate an accurate fan speed count value. The following
equation can be used to determine the current RPM value of the fan:
RPM = (1,200,000)/(Decimal-Count-Value X Divisor)
When the result of a read of this register is 00h, an accurate fan speed count value
has not been generated indicating that the fan has not completed a minimum of one
revolution. When the result of a read of this register is FFh, the fan is rotating very
slowly or there are no tachometer pulses present. When operating in a polled mode
with the FSIEN bit reset in the FSC2 register, this register will automatically update
with an accurate fan speed count once per revolution of the fan. When operating in
an interrupt mode with the FSIEN bit set in the FSC2 register, this register will auto-
matically update with an accurate fan speed count once per revolution of the fan
until an interrupt is generated. Once the interrupt is generated, the value will remain
stable until the interrupt is cleared. When the interrupt is cleared, this register will
also be cleared indicating that a valid RPM value is in the process of being gener-
ated.
Revision 4.0
November 10, 2004
4-31