ISM 868 MHz, 433 MHz and 315 MHz FSK Transmitter – Preliminary Data Sheet

ASCell3911

Rev. A, February 2000

Page 7 of 13

Austria Mikro Systeme International AG

The ASCell3911 WAKEUP pin is active and set to ”L”, holding the µC in reset state. In standby

mode the ASCell3911 WAKEUP internal pull-up is disabled and does not drain current from the

supply.

The ASCell3911 µC_CLK output is disabled, (in high resistive ”Z” state) and internally pulled up

to ”H”.

(Re)starting the transmitter: Closing the push button (giving a falling edge on µC_CLK line)

starts up the ASCell3911. It turns on its XTAL oscillator and after the oscillator start up phase it

turns the µC_CLK pin to active (CMOS level) mode and provides a clock to the µC.

After a delay of 32 µC clock cycles the WAKEUP pin of the ASCell3911 is set to ”H” for 16 clock

cycles. The transmitter is now in active mode. The WAKEUP acts in ASCell3911 active mode

as an input waiting for a ”L” to trigger the transmission of the transmitter to standby mode

During this active mode the µC sends the 132 bit data (8 bit control and 16 * 8 bit data) on the

µC - P1 (Serial data out) line.

The timing of the microcontroller interface is shown in Figure 5. The microcontroller clocks a

134-bit Data into the ASCell3911 for data encoding. This data consists of 6 control bits followed

by 128 transmit data bits. After the data bock has been completely transferred to the AS-

Cell3911, it starts up transmission, during which the I/Q modulator and power amplifier are pow-

ered up in order to transmit the encoded data. Transmission is done with respect to the control

bits. Table 2 shows the control bits set different operation modes of the chip.

wake up

DATA

D_CLK

TX-State

t

P4

standby

active

transmission

standby

start

transmission

stop

transmission

D_EN

startup/reset µC

SMT

Figure 5:

µC interface timing for data transmission when ASCell3911 and µC are active.

Note:

Figure 4 shows the timing for the CMT-mode where the controller sets P4 to “L” and so the transmission stops. The

broken line shows the Signal P4 in the SMT mode where the ASCell3911 stops the transmission.

Control bit description:

bit#

Name

Comments

1

Quartz crystal (“CRYSTAL”):

L=13,5600 / 13,5672MHz

H=19,6875 MHz

2

Operating frequency range (“RANGE”):

L=315/433MHz,

H=868,3MHz

3

Duty cycle operation (“DCO”)

L = OFF

H = ON

4

Single / Continuous Message Transmission

(“SMT/CMT”)

L = SMT

H = CMT