Texas Instruments TRF7970A Manual page 46

TRF7970A
SLOS743L – AUGUST 2011 – REVISED MARCH 2017
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
• 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).
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.
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.
46 Detailed Description
Figure 6-28, this step is TRF7970A specific)
NOTE
NOTE
NOTE
Figure 6-28. Entering Direct Mode 0
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