MC33690 Datasheet, PDF (10/24 Pages) Motorola, Inc – Standalone Tag Reader Circuit

Freescale S^Me^Cm³³i⁶c⁹o⁰nductor, Inc.
STANDALONE CONFIGURATION WITH ONE WIRE BUS
When a low level is applied on pins MODE1
and MODE2, the circuit is in configuration A
(standalone single wire bus configuration, see
figure 13 page 18).
After power on, the circuit is set into read mode.
The demodulator output is directly routed to the
ISO 9141 interface output K.
The circuit can be set into write mode at anytime
by violation of all possible patterns on the single
wire bus during more than 1ms. Then the K line
achieves the amplitude modulation by switching
on/off both antenna drivers.
After 1ms of inactivity at the end of the challenge
phase (bus in idle recessive one state), the circuit
is set back into read mode.
The circuit can be put into standby mode by
forcing the K line at zero during more than 2 ms
after entering the write mode. Once the K line is
released, 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 K. The driver
output TD1 forces a low level and TD2 a high
level. A rising edge on K wakes up the circuit.
After completion of the wake-up sequence, the
circuit is automatically set in read mode.
In configuration A, DOUT and Rx outputs always
force a low level, Tx is disabled.
Figure 6 : Mode access description in one wire bus configuration
Read to write mode :
K line
read mode
T₀ ≤ t < T₀’+T₁’
1
1
1
0
0
0
write mode
Write to read mode :
K line
write mode
Write to standby mode :
K line
write mode
Standby mode to read mode :
t ≥T₀
t ≥ T₁
T₂
T₂
acknowledge
read mode
standby mode
K line
standby mode
wake-up sequence
read mode
reset
Figure 7 : Configuration A state diagram
T₀ ≤ K line low
read
write
TD1/2 off
K line high < T₀’
T₀ ≤ K line high
K line low
wake up
T₁ ≤ K line low
K
standby
write
TD1/2
switching
© Motorola, Inc., 2002.
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revision 4.8, 5 February 2002