User's Manual

Table Of Contents

TRF7970A

www.ti.com

SLOS743K –AUGUST 2011–REVISED APRIL 2014

• Send the transmit command and the number of bytes to be transmitted first, and then start to send the

data to the FIFO. The transmission starts when first data byte is written into the FIFO.

NOTE

If the data length is longer than the FIFO, the TRF7970A notifies the external system MCU

when most of the data from the FIFO has been transmitted by sending an interrupt request

with a flag in the IRQ register to indicate a FIFO low or high status. The external system

should respond by loading the next data packet into the FIFO.

At the end of a transmit operation, the external system MCU is notified by interrupt request (IRQ) with a

flag in IRQ register (0x0C) indicating TX is complete (example value = 0x80).

The TX Length registers also support incomplete byte transmission. The high two nibbles in register 0x1D

and the nibble composed of bits B4 through B7 in register 0x1E store the number of complete bytes to be

transmitted. Bit B0 in register 0x1E is a flag indicating that there are also additional bits to be transmitted

that do not form a complete byte. The number of bits is stored in bits B1 through B3 of the same register

(0x1E).

Some protocols have options, and there are two sublevel configuration registers to select the TX protocol

options.

• ISO14443B TX Options register (0x02). This register controls the SOF and EOF selection and EGT

selection for the ISO14443B protocol.

• ISO14443A High Bit Rate Options and Parity register (0x03). This register enables the use of different

bit rates for RX and TX operations in the ISO14443 high bit rate protocol and also selects the parity

method in the ISO14443A high bit rate protocol.

The digital section also has a timer. The timer can be used to start the transmit operation at a specified

time in accordance with a selected event.

6.9 Transmitter – External Power Amplifier and Subcarrier Detector

The TRF7970A can be used in conjunction with an external TX power amplifier or external subcarrier

detector for the receiver path. In this case, certain registers must be programmed as shown here:

• Bit B6 of the Regulator and I/O Control register (0x0B) must be set to 1. This setting has two functions:

first, to provide a modulated signal for the transmitter if needed, and second, to configure the

TRF7970A receiver inputs for an external demodulated subcarrier input.

• Bit B3 of the Modulation and SYS_CLK Control register (0x09) must be set to 1 (see

Section 6.14.3.2.8). This function configures the ASK/OOK pin for either a digital or analog output (B3

= 0 enables a digital output, B3 = 1 enables an analog output). The design of an external power

amplifier requires detailed RF knowledge. There are also readily designed and certified high-power HF

reader modules on the market.

Submit Documentation Feedback

Product Folder Links: TRF7970A