Si1000/1/2/3/4/5
D7
D6
D5
D4
D3
D2
D1
D0
POR
Def.
Add R/W Function/Description
14 R/W Wake-Up Timer Period 1
wtr[4]
wtr[3]
wtr[2]
wtr[1] wtr[0]
03h
15 R/W Wake-Up Timer Period 2 wtm[15] wtm[14] wtm[13] wtm[12] wtm[11] wtm[10] wtm[9] wtm[8] 00h
16 R/W Wake-Up Timer Period 3 wtm[7] wtm[6] wtm[5] wtm[4] wtm[3] wtm[2] wtm[1] wtm[0] 00h
17
18
R
R
Wake-Up Timer Value 1 wtv[15] wtv[14] wtv[13] wtv[12] wtv[11] wtv[10] wtv[9] wtv[8]
Wake-Up Timer Value 2 wtv[7] wtv[6] wtv[5] wtv[4] wtv[3] wtv[2] wtv[1] wtv[0]
—
—
There are two different methods for utilizing the wake-up timer (WUT) depending on if the WUT interrupt is
enabled in “Register 06h. Interrupt Enable 2.” If the WUT interrupt is enabled then nIRQ pin will go low
when the timer expires. The chip will also change state so that the 30 MHz XTAL is enabled so that the
microcontroller clock output is available for the microcontroller to use to process the interrupt. The other
method of use is to not enable the WUT interrupt and use the WUT GPIO setting. In this mode of operation
the chip will not change state until commanded by the microcontroller. The different modes of operating the
WUT and the current consumption impacts are demonstrated in Figure 23.23.
A 32 kHz XTAL may also be used for better timing accuracy. By setting the x32 ksel bit in Register 07h
"Operating & Function Control 1", GPIO0 is automatically reconfigured so that an external 32 kHz XTAL
may be connected to this pin. In this mode, the GPIO0 is extremely sensitive to parasitic capacitance, so
only the XTAL should be connected to this pin with the XTAL physically located as close to the pin as pos-
sible. Once the x32 ksel bit is set, all internal functions such as WUT, microcontroller clock, and LDC mode
will use the 32 kHz XTAL and not the 32 kHz RC oscillator.
The 32 kHz XTAL accuracy is comprised of both the XTAL parameters and the internal circuit. The XTAL
accuracy can be defined as the XTAL initial error + XTAL aging + XTAL temperature drift + detuning from
the internal oscillator circuit. The error caused by the internal circuit is typically less than 10 ppm.
276
Rev. 1.0
SILICON [ SILICON ]
