11
ATA5580 [DATASHEET]
9254E–RKE–08/14
2.6 Device Initialization
This section describes how the transponder device handles the initial power-up sequence. The outcome or determination
from the initialization sequence depends on various conditional paths. These are described in the following sections. The
system can guarantee that the immobilizer functionality is given the highest priority and can operate independently from the
application code by means of this initialization sequence.
2.6.1 Power-up Scenarios
Power-up occurs whenever there is a reset event. This can be power-on-reset (POR), external reset, watchdog reset,
brown-out reset, and transponder reset. All registers, ports, and SRAM are set to initial conditions during the reset. The
program counter is always set to the reset vector located in the bootloader section. This ensures the priority of the
immobilizer over all other functions. After a fixed delay, a code is executed to check the conditions described as follows.
2.6.2 LF Field De te ct io n
The very first item checked after the reset delay is the determination of the presence of an LF field. If the LF field is present,
then the immobilizer function is used and the other conditional checks can be skipped and the immobilizer function executed.
If the LF field is NOT present, the initialization routine will eventually exit to the application code section after the next step.
Transponder initialization will not occur.
2.6.3 Enhanced Mode Detection
This command does not apply to the Atmel® ATA5580 and is ignored.
2.6.4 Transponder Initialization
Once all conditions have been met for entering transponder mode, the following items are configured to prepare for
communication:
●The presence of an LF field has to be acknowledged in order to enable operation of the transponder
●System clocks are reconfigured
●System resources are configured for the lowest power consumption possible
●The interrupt vector table is mapped into bootloader space
●The watchdog timer is configured and activated
●System resources for uplink and downlink communication processing are initialized
2.6.5 Reliable Communication Channel Indication
Once the device has been initialized for transponder mode, an indication of this readiness can be conveyed to the base
station if selected during device configuration. This is achieved through the transmission of a detection header that ensures
with high probability that the communication channel is open and reliable. Both the uplink and downlink paths are verified by
this in the manner described here.
For the downlink to be successful, the transponder must receive enough power to operate. Once this condition is satisfied for
a long enough time to charge a buffer capacitor, the transponder can survive field gaps needed to transfer data. The fact that
the initialization routine was successfully executed up to this point means it has been achieved.
For the uplink to be successful, the transponder must modulate the carrier field with sufficient coupling and modulation depth
for the base station to be able to recover the data from the carrier. By sending a modulated signal as defined by the detection
header, the base station can make a determination that the uplink path is open once the header is visible on the
demodulated output.
2.7 LF Physical Layer
All communication between the base station and the transponder occurs using the LF field as the signal carrier. The LF
communication link is established when the transponder transmits the LF channel detection header consisting of a
Manchester coded sequence of “1010…” as a 125kHz signal which continues until the base station interrupts the signal
during a damped phase with a gap.
The physical layer (uplin k and downlink) is compatible with all sta nd ard FDX bas e station s availab le o n the ma rket.