User's Manual

Table Of Contents

TRF7970A

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SLOS743K –AUGUST 2011–REVISED APRIL 2014

Communication is initialized by a start condition, which is expected to be followed by an

Address/Command word (Adr/Cmd). The Adr/Cmd word is 8 bits long, and Table 6-11 shows its format.

Table 6-11. Address and Command Word Bit Distribution

Bit Description Bit Function Address Command

0 = address

B7 Command control bit 0 1

1 = command

0 = write

B6 Read/Write R/W 0

1 = read

B5 Continuous address mode 1 = Continuous mode R/W 0

B4 Address/Command bit 4 Adr 4 Cmd 4

B3 Address/Command bit 3 Adr 3 Cmd 3

B2 Address/Command bit 2 Adr 2 Cmd 2

B1 Address/Command bit 1 Adr 1 Cmd 1

B0 Address/Command bit 0 Adr 0 Cmd 0

The MSB (bit 7) determines if the word is to be used as a command or as an address. The last two

columns of Table 6-11 show the function of the separate bits if either address or command is written. Data

is expected once the address word is sent. In continuous-address mode (Cont. mode = 1), the first data

that follows the address is written (or read) to (from) the given address. For each additional data, the

address is incremented by one. Continuous mode can be used to write to a block of control registers in a

single stream without changing the address; for example, setup of the predefined standard control

registers from the MCU non-volatile memory to the reader. In non-continuous address mode (simple

addressed mode), only one data word is expected after the address.

Address Mode is used to write or read the configuration registers or the FIFO. When writing more than 12

bytes to the FIFO, the Continuous Address Mode should be set to 1.

The Command Mode is used to enter a command resulting in reader action (for example, initialize

transmission, enable reader, and turn reader on or off).

Examples of expected communications between an MCU and the TRF7970A are shown in the following

sections.

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