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SLOS743L – AUGUST 2011 – REVISED MARCH 2017
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Detailed Description
Copyright © 2011–2017, Texas Instruments Incorporated
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
shows its format.
Table 6-11. Address and Command Word Bit Distribution
BIT
DESCRIPTION
BIT FUNCTION
ADDRESS
COMMAND
B7
Command control bit
0 = Address
1 = Command
0
1
B6
Read/Write
0 = Write
1 = Read
R/W
0
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
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 nonvolatile memory to the reader. In noncontinuous 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.
Command Mode is used to enter a command resulting in reader action (for example, initialize
transmission, enable reader, and turn reader on or off).
The following sections give examples of the expected communications between an MCU and the
TRF7970A.
