MC33690 データシートの表示（PDF） - Freescale Semiconductor
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MC33690 Datasheet PDF : 26 Pages
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Standalone Configuration with Two-Wire Bus
8 Standalone Configuration with Two-Wire Bus
When a low level is applied on MODE1 and a high level on MODE2, the circuit is in configuration B (see Figure 25). 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. This amplitude
modulation can be monitored on the K output and 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
and ISO 9141 driver) are inactive except for 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 and Tx is disabled.
Read and write sequences: drivers on
AM line
K line
data read
Entering into standby mode:
AM line
t Š T1
K line
T1
acknowledge
T2
T2
drivers off
data write modulation
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 8. Modes Access Description in Two-wire Bus Configuration
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
Figure 9. Configuration B State Diagram
MC33690 Standalone Tag Reader Circuit, Rev. 5
12
Freescale Semiconductor
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