ATA5279 ATMEL Corporation, ATA5279 Datasheet - Page 20

• Manufacturer Part Number: ATA5279
• Manufacturer: ATMEL Corporation

20
ATA5279 [Preliminary]
In this example, the output signal of the modulator resembles the illustration below.
Figure 3-14. Example of Data Transmission of Two Consecutive Commands
The value for t
22 periods in high speed mode, with one period being 8 µs when operating with 125 kHz output
frequency and therefore 8 MHz system clock).
The least amount of data that can be processed by the modulator stage is four LF bits or two
(e.g. Manchester-encoded) data bits. The first command in the upper example is a mini-
mum-length LF data command.
To ensure the traceability of the LF protocol, two pins are provided, which indicate an active data
transmission (MACT) and the change of an LF bit (BCNT).
these two signals:
Figure 3-15. LF Transmission Tracing Signals
The MACT signal can be used to start a timer whereas BCNT can be used as input signal to a
counter. Note that for carrier transmissions, only the MACT signal is active. There are not any
pulses on the BCNT line.
Transmitter Coil Current
Modulator Data
Modulator Data
BCNT Signal
MACT Signal
BCNT Signal
data
depends on the speed setting of the modulator (32 LF-periods in standard and
off
First Command
1
2
t
data
0
Current Envelope
1
26
1
t
data
Second Command
Figure 3-13
24
0
t
data
1
illustrates the function of
1
9125A–RKE–04/08
off