FXTH870xD
Sensors
88
Freescale Semiconductor, Inc.
11.2
Wakeup Divider Register - PWUDIV
The PWUDIV register contains six bits to select the division of the incoming 1 ms clock period as described in
Figure 61
.
11.3
PWU Control/Status Register 0 - PWUCS0
The PWUCS0 register contains six bits to select the division of the incoming WCLK clock period and provide interrupt flag and
acknowledge bits as described in
Figure 62
. The period of the resulting interrupt also generates the clock, RCLK, for the periodic
reset timing.
$0038
Bit 7
6
5
4
3
2
1
Bit 0
R
0
0
WDIV[5:0]
W
RESET:
—
—
—
—
—
—
—
—
POR:
0
0
0
1
1
1
1
1
= Reserved
Figure 61. PWU Divider Register (PWUDIV)
Table 54. PWUDIV Register Field Descriptions
Field
Description
7:6
Unused
Unused
5:0
WDIV[5:0]
Wakeup Divider Value
— The WDIV[5:0] bits select an incoming prescaler for the incoming 1 ms clock period from 504 to 1512.
This results in a clocking of the 6-bit wakeup divider at rates from a nominal 0.504 to 1.512 sec per wakeup clock, WCLK. The
user can use this prescaler to fine tune the wakeup time based on the variation in the LFO frequency. The conversion from the
decimal value of the WDIV bits to the nominal WCLK period is given as:
A power on reset presets these bits to a value of $1F (decimal 31) which yields a nominal 1 second output period for WCLK.
Other resets have no effect on these bits.
$0039
Bit 7
6
5
4
3
2
1
Bit 0
R
WUF
0
WUT[5:0]
W
WUFAK
RESET:
0
—
1
1
1
1
1
1
Figure 62. PWU Control/Status Register 0 (PWUCS0)
Table 55. PWUSC0 Register Field Descriptions
Field
Description
7
WUF
Wakeup Interrupt Flag
— The WUF bit indicates when a wakeup interrupt has been generated by the PWU. This bit is cleared
by writing a one to the WUFAK bit. Writing a zero to this bit has no effect. Reset clears this bit.
0
Wakeup interrupt not generated or was previously acknowledged.
1
Wakeup interrupt generated.
6
WUFAK
Acknowledge WUF Interrupt Flag
— The WUFAK bit clears the WUF bit if written with a one. Writing a zero to the WUFAK bit
has no effect on the WUF bit. Reading the WUFAK bit returns a zero. Reset has no effect on this bit.
0
No effect.
1
Clear WUF bit.
t
WCLK
504
16
WDIV
+
f
LFO
-------------------------------------------------
=
Summary of Contents for FXTH870 D Series
Page 86: ...FXTH870xD Sensors 84 Freescale Semiconductor Inc Figure 57 Data Flow For Measurements...
Page 171: ...FXTH870xD Sensors Freescale Semiconductor Inc 169 Figure 128 QFN Case Outline...
Page 172: ...FXTH870xD Sensors 170 Freescale Semiconductor Inc Figure 129 QFN Case Outline...
Page 173: ...FXTH870xD Sensors Freescale Semiconductor Inc 171...
