Si4020
SIMPLIFIED INTERNAL CONTROL AND TIMING
The internal controller uses the clock generated by the crystal oscillator to sequentially process the various events and to de-bounce
the push-button (PB) inputs. If the oscillator is not running, internal logic automatically turns it on temporarily and then off again.
Such events are: any wake-up event (POR, PB press, wake-up timer timeout, and low supply voltage detection), PB release and
status read request by the microcontroller.
If two wake-up events occur in succession, the crystal oscillator stays on until the next status read (acknowledgment of the first
event).
Simplified Internal Control and Timing Diagrams
Microcontroller mode (ec=0, ex=0)
Vdd
POR
(internal)
Push-button
inpu t x
Debouncing Time + T sx*
Osc_On
(In terna l)
SPI
Status rd cmd
Status rd cmd
nIRQ
Stat. b its
(PO R)
Stat. b its
(PB x)
Tsx*
Tsx*
Microcontroller modewith multiple event read (ec=0, ex=0)
Vdd
POR
(internal)
Push-button
inpu t x
Osc_On
(In terna l)
SPI
Status rd cmd
Status rd cmd
nIRQ
Stat. b its
(PO R)
Stat. b its
(PB x)
1us
Tsx*
Microcontroller mode (ec=1, ex=0)
Vdd
POR
(internal)
Push-button
inpu t x
Osc_On
(In terna l)
SPI
Status rd
Slee p cmd
Status rd
Sleep cmd
Tclk_tail**
Tclk_tail**
Note:
Tsx : Crystal oscillator st
*
artup t ime
** Length of Tclk_tail is determined by the parameter in the Sleep comm
a nd
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SILICON [ SILICON ]
