MaximIntegrated 10-5
MAX31782 User’s Guide
Revision 0; 8/11
10.2.2TachometerValueRegister(TACHVn)
The tachometer value register, TACHVn, holds the 16-bit value of the tachometer’s up-counting timer . Enabling/dis-
abling the tachometer with the TACHE bit does not reset this count value; it must be cleared explicitly by software . This
register is cleared to 0000h on all forms of reset and has unrestricted read/write access .
10.2.3TachometerCaptureRegister(TACHRn)
The tachometer capture register, TACHRn, stores the 16-bit value in TACHVn when a tachometer capture occurs . The
TACHRn value indicates how many prescaled system clock pulses occurred during one revolution of the fan, assum-
ing the revolution prescaler is set correctly . The value in TACHRn is typically used to calculate fan speed in fan control
applications . This register is cleared to 0000h on all forms of reset and has unrestricted read/write access .
10.2.3TachometerRegisterLocations
The addresses for the tachometer registers are given as “Mx[yy],” where x is the module number (from 0 to 5 decimal)
and yy is the register index (from 00h to 1Fh hexadecimal) .
shows the address for these registers for each
of the six tachometer blocks (TACH .n) .
Table10-1.TachometerRegisterAddresses
Table10-2.Tachometer/GPIOPinMultiplexingInputPins
10.3TachometerPinandGPIOMultiplexing
When the tachometer’s pin functionality is disabled (TEXEN = 0), that pin can be used as a GPIO . The tachometer
pins are mapped to GPIO port P2[5:0] .
shows the mapping of the MAX31782 tachometer pins . Refer to
SECTION 11: General-Purpose Input/Output (GPIO) Pins
for information on using the tachometer pins as GPIO .
REGISTERNAME
INDIVIDUALTACHOMETERNUMBER
n=0
n=1
n=2
n=3
n=4
n=5
TACHCNn
M3[0Dh]
M3[0Fh]
M4[0Dh]
M4[0Fh]
M5[0Dh]
M5[13h]
TACHRn
M3[05h]
M3[07h]
M4[05h]
M4[07h]
M5[0Fh]
M5[11h]
TACHVn
M3[0Ch]
M3[0Eh]
M4[0Ch]
M4[0Eh]
M5[0Ch]
M5[12h]
TACHOMETERINPUTPIN
MAX31782PIN
GPIOPIN
TACH .0
30
P2 .0
TACH .1
27
P2 .1
TACH .2
25
P2 .2
TACH .3
23
P2 .3
TACH .4
19
P2 .4
TACH .5
17
P2 .5
