si4021 Silicon Laboratories, si4021 Datasheet - Page 18

• Manufacturer Part Number: si4021
• Description: Si4021 Universal Ism Band Fsk Transmitter
• Manufacturer: Silicon Laboratories

Simultaneously Pressed Push-Button Detect by Microcontroller
Simplified Block Diagram of Push-Button 1–4 Inputs
Push button
Push button
(internal)
nIRQ
input 1
input 2
Push-button1,2,3
SPI
POR
Vdd
Microcontroller mode
Push-button4
p4
Status rd
Push-button1
Push-button2
POR
With internal weak pull-up
VDD
ENABLE/DISABLE
WEAK PULL-UP
CLK
blocker signal
PB_nIRQdly*
Push-button1
Push-button2
Status rd
Internal
and
to
PB1
Digital glitch
CLR for P.B1,2
bc
Status rd
filter
PB1
VDD
To Digital glitch filter for
Status rd
Push-button4
PB2
POR, LBD, WAKE UP TIMER,
P. BUTTONS EVENT FLAGS
Status rd
D
CLR
PB1
Q
Status rd
PB2
Note:
*PB_nIRQdly is equal with the
debounce time
Status rd
Note:
STAT. REG. READ Command **
** In uC controlled mode
PB1
* In EEprom mode
Notice:
Only one EVENT is
serviced simultaneously
the others are pending.
SLEEP Command *
COUNT/SINGLE
EVENT FLAG
b1, b2, b3
IA4221
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