MC33690 Datasheet, PDF (12/24 Pages) Motorola, Inc – Standalone Tag Reader Circuit

Freescale S^Me^Cm³³i⁶c⁹o⁰nductor, Inc.
STANDALONE CONFIGURATION WITH TWO WIRES BUS
When a low level is applied on MODE1 and a
high level on MODE2, the circuit is in
configuration B (standalone 2 wires bus
configuration, see figure 14 page 19).
The K pin is set as an output sending the
demodulated data.
The AM pin is set as a VSUP referenced input pin
receiving the amplitude modulation and the
shutdown/wake-up commands. Forcing high and
low levels on AM achieves the amplitude
modulation by switching on/off both antenna
drivers. Meanwhile, this amplitude modulation
can be monitored on the K output. This allows
antenna short and open circuit diagnosis.
The circuit can be put into standby mode by
forcing the AM line at zero during more than 2
ms. The circuit sends an acknowledge pulse
before entering into standby mode
In standby mode, the oscillator and most of the
internal biasing currents are switched off.
Therefore, the functions (tag reader, ISO 9141
driver) are inactive except the voltage regulator
and the ISO 9141 receiver on pin AM. The driver
output TD1 forces a low level and TD2 a high
level. A rising edge on AM wakes up the circuit.
After completion of the wake-up sequence, the
circuit is automatically set in read mode.
In configuration B, DOUT and Rx outputs always
force a low level, Tx is disabled.
Figure 8 : Modes access description in two wires bus configuration
Read & write sequences : _{drivers on}
drivers off
data write modulation
AM line
K line
data read
Entering into standby mode :
AM line
t ≥ T1
K line
T1
acknowledge
T2
T2
1
1
1
0
0
0
data write
1
1
1
0
0
0
AM line monitoring
standby mode
Coming out of standby mode :
AM line
standby mode
wake-up sequence
data read
K line
Figure 9 : Configuration B state diagram
reset
TD1/2
switching
AM line low
AM line high
wake up
AM line high
TD1/2 off
AM line low
T1 ≤ AM line low
AM
standby
© Motorola, Inc., 2002.
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revision 4.8, 5 February 2002