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SLOS743L – AUGUST 2011 – REVISED MARCH 2017
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Detailed Description
Copyright © 2011–2017, Texas Instruments Incorporated
The steps to enter direct mode are listed below, using SPI with SS communication method only as one
example, as direct modes are also possible with parallel and SPI without SS. The must enter direct mode
0 to accommodate card type communications that are not compliant with ISO standards. Direct mode can
be entered at any time, so if a card type started with ISO standard communications, then deviated from
the standard after being identified and selected, the ability to go into direct mode 0 is very useful.
Step 1: Configure Pins I/O_0 to I/O_2 for SPI with SS
Step 2: Set Pin 12 of the TRF7970A (ASK/OOK pin) to 0 for ASK or 1 for OOK
Step 3: Program the TRF7970A registers
The following registers must be explicitly set before going into the direct mode.
1. ISO Control register (0x01) to the appropriate standard
–
0x02 for ISO/IEC 15693 High Data Rate
–
0x08 for ISO/IEC 14443 A (106 kbps)
–
0x1A for FeliCa 212 kbps
–
0x1B for FeliCa 424 kbps
2. Modulator and SYS_CLK register (0x09) to the appropriate clock speed and modulation
–
0x21 for 6.78 MHz Clock and OOK (100%) modulation
–
0x20 for 6.78 MHz Clock and ASK 10% modulation
–
0x22 for 6.78 MHz Clock and ASK 7% modulation
–
0x23 for 6.78 MHz Clock and ASK 8.5% modulation
–
0x24 for 6.78 MHz Clock and ASK 13% modulation
–
0x25 for 6.78 MHz Clock and ASK 16% modulation
(See register 0x09 definition for all other possible values)
Example register setting for ISO/IEC 14443 A at 106 kbps:
•
ISO Control register (0x01) to 0x08
•
RX No Response Wait Time register (0x07) to 0x0E
•
RX Wait Time register (0x08) to 0x07
•
Modulator control register (0x09) to 0x21 (or any custom modulation)
•
RX Special Settings register (0x0A) to 0x20