Si1000/1/2/3/4/5
23.7. RX Modem Configuration
A Microsoft Excel parameter calculator or Wireless Development Suite (WDS) calculator is provided to
determine the proper settings for the modem. The calculator can be found on www.silabs.com or on the
CD provided with the demo kits. An application note is available to describe how to use the calculator and
to provide advanced descriptions of the modem settings and calculations.
23.7.1. Modem Settings for FSK and GFSK
The modem performs channel selection and demodulation in the digital domain. The channel filter band-
width is configurable from 2.6 to 620 kHz. The receiver data-rate, modulation index, and bandwidth are set
via registers 1C–25h. The modulation index is equal to 2 times the peak deviation divided by the data rate
(Rb).
When Manchester coding is disabled, the required channel filter bandwidth is calculated as BW = 2Fd + Rb
where Fd is the frequency deviation and Rb is the data rate.
23.8. Auxiliary Functions
The EZRadioPRO has some auxiliary functions that duplicate the directly accessible MCU peripherals:
ADC, temperature sensor, and 32 kHz oscillator. These auxiliary functions are retained primarily for com-
patibility with the Si4430/1/2. The directly accessed MCU peripherals typically provide lower system cur-
rent consumption and better analog performance. However some of these EZRadioPRO auxiliary
functions offer features not directly duplicated in the MCU directly accessed peripherals, such as the Low
Duty Cycle Mode operation.
23.8.1. Smart Reset
The EZRadioPRO transceiver contains an enhanced integrated SMART RESET or POR circuit. The POR
circuit contains both a classic level threshold reset as well as a slope detector POR. This reset circuit was
designed to produce a reliable reset signal under any circumstances. Reset will be initiated if any of the fol-
lowing conditions occur:
Initial power on, V starts from gnd: reset is active till V reaches V (see table);
DD DD RR
When V decreases below V for any reason: reset is active till V reaches V ;
RR
DD
LD
DD
A software reset via “Register 08h. Operating Mode and Function Control 2”: reset is active for time
T
SWRST
On the rising edge of a V glitch when the supply voltage exceeds the following time functioned limit:
DD
VDD nom.
VDD(t)
reset limit:
0.4V+t*0.2V/ms
actual VDD(t)
showing glitch
0.4V
Reset
TP
t
t=0,
reset:
VDD starts to rise
Vglitch>=0.4+t*0.2V/ms
Figure 23.20. POR Glitch Parameters
Rev. 1.0
269
SILICON [ SILICON ]
