si4021 Silicon Laboratories, si4021 Datasheet - Page 17

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

8. Push-Button Command
If the corresponding bit was set (b1-b4) the event remains active while the button is pressed. In EEPROM mode, the chip is continuously
performing the routine assigned to the push-button while it is pressed. In microcontroller mode, the chip continuously generates interrupts
on nIRQ until the push-button is released. Weak pull-up currents are switched off when bc is high.
The d0, d1 bits set the de-bouncing time period:
Note:
bit
•
•
•
d1
0
0
1
1
15
1
Until the de-bouncing time has expired, the crystal oscillator remains switched on, independent of the status of the ex bit in the
Power Management Command. (Because the circuit uses the crystal oscillator signal for timing.)
If the p4 bit is set, the controller performs the routine assigned to the fourth button when PB1 and PB2 are pressed down
simultaneously. With the addition of this feature, there is a way to build a device that uses 3 buttons, but performs 4 functions.
It is possible to detect multiple pressed push-buttons, in both modes. In EEPROM mode the controller executes sequentially all the
routines belonging to the pressed buttons.
d0
0
1
0
1
14
1
De-bouncing Time [ms]
160
40
10
0 (Bypassed)
13
0
12
0
11
1
10
0
9
1
8
0
p4
7
d1
6
d0
5
b4
4
b3
3
b2
2
b1
1
bc
0
CA00h
POR
IA4221
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