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SLOS743L – AUGUST 2011 – REVISED MARCH 2017
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Detailed Description
Copyright © 2011–2017, Texas Instruments Incorporated
Step 4: Entering Direct Mode 0
The following registers must be programmed to enter direct mode 0:
1. Set bit B6 of the Modulator and SYS_CLK Control register (0x09) to 1.
2. Set bit B6 of the ISO Control (Register 01) to 0 for direct mode 0 (default its 0)
3. Set bit B6 of the Chip Status Control register (0x00) to 1 to enter direct mode
4. Send extra eight clock cycles (see
, this step is TRF7970A specific)
NOTE
•
It is important that the last write is not terminated with a stop condition. For SPI, this
means that Slave Select (I/O_4) stays low.
•
Sending a Stop condition terminates the direct mode and clears bit B6 in the Chip Status
Control register (0x00).
NOTE
Access to Registers, FIFO, and IRQ is not available during direct mode 0.
The reader enters the direct mode 0 when bit 6 of the Chip Status Control register (0x00) is set to a 1 and
stays in direct mode 0 until a stop condition is sent from the microcontroller.
NOTE
The write command should not be terminated with a stop condition (for example, in SPI
mode this is done by bringing the Slave Select line high after the register write), because the
stop condition terminates the direct mode and clears bit 6 of the Chip Status Control register
(0x00), making it a 0.
Figure 6-28. Entering Direct Mode 0