Si1000/1/2/3/4/5
TX, or RX states. When the chip enters SLEEP mode, the output clock will automatically switch to
32.768 kHz from the RC oscillator or 32.768 XTAL.
Another available feature for the output clock is the clock tail, clkt[1:0] in “Register 0Ah. Microcontroller
Output Clock." If the low frequency clock feature is not enabled (enlfc = 0), then the output is disabled in
SLEEP mode. Setting the clkt[1:0] field will provide additional cycles of the output clock before it shuts off.
clkt[1:0]
Modulation Source
0 cycles
00
01
10
11
128 cycles
256 cycles
512 cycles
If an interrupt is triggered, the output clock will remain enabled regardless of the selected mode. As soon
as the interrupt is read the state machine will then move to the selected mode. The minimum current con-
sumption will not be achieved until the interrupt is read. For instance, if the EZRadioPRO peripheral is
commanded to SLEEP mode but an interrupt has occurred the 30 MHz XTAL will not be disabled until the
interrupt has been cleared.
23.8.3. General Purpose ADC
The EZRadioPRO peripheral includes an 8-bit SAR ADC independent of ADC0. It may be used for general
purpose analog sampling, as well as for digitizing the EZRadioPRO temperature sensor reading. In most
cases, the ADC0 subsystem directly accessible from the MCU will be preferred over the ADC embedded
inside the EZRadioPRO peripheral. Registers 0Fh "ADC Configuration", 10h "Sensor Offset" and 4Fh
"Amplifier Offset" can be used to configure the ADC operation. Details of these registers are in “AN440:
EZRadioPRO Detailed Register Descriptions.”
Every time an ADC conversion is desired, bit 7 "adcstart/adcdone" in Register 0Fh “ADC Configuration”
must be set to 1. The conversion time for the ADC is 350 µs. After the ADC conversion is done and the
adcdone signal is showing 1, then the ADC value may be read out of “Register 11h: ADC Value." When the
ADC is doing its conversion, the adcstart/adcdone bit will read 0. When the ADC has finished its conver-
sion, the bit will be set to 1. A new ADC conversion can be initiated by writing a 1 to the adcstart/adcdone
bit.
The architecture of the ADC is shown in Figure 23.21. The signal and reference inputs of the ADC are
selected by adcsel[2:0] and adcref[1:0] in register 0Fh “ADC Configuration”, respectively. The default set-
ting is to read out the temperature sensor using the bandgap voltage (VBG) as reference. With the VBG
reference the input range of the ADC is from 0–1.02 V with an LSB resolution of 4 mV (1.02/255). Chang-
ing the ADC reference will change the LSB resolution accordingly.
A differential multiplexer and amplifier are provided for interfacing external bridge sensors. The gain of the
amplifier is selectable by adcgain[1:0] in Register 0Fh. The majority of sensor bridges have supply voltage
(VDD) dependent gain and offset. The reference voltage of the ADC can be changed to either V /2 or
DD
V
/3. A programmable V dependent offset voltage can be added using soffs[3:0] in register 10h.
DD
DD
Rev. 1.0
271
SILICON [ SILICON ]
