Texas Instruments TRF7970A Instruction Manual page 31

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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
Bit
B7
B6
B5
B4
B3
B2
B1
B0
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
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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Table 6-11. Address and Command Word Bit Distribution
Description
Command control bit
Read/Write
Continuous address mode
Address/Command bit 4
Address/Command bit 3
Address/Command bit 2
Address/Command bit 1
Address/Command bit 0
show the function of the separate bits if either address or command is written. Data
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SLOS743K – AUGUST 2011 – REVISED APRIL 2014
Table 6-11
Bit Function Address
0 = address
1 = command
0 = write
R/W
1 = read
1 = Continuous mode R/W
Adr 4
Adr 3
Adr 2
Adr 1
Adr 0
TRF7970A
TRF7970A
shows its format.
Command
0 1
0
0
Cmd 4
Cmd 3
Cmd 2
Cmd 1
Cmd 0
Detailed Description 31