ZHCS363L August 2011 – March 2017 TRF7970A
PRODUCTION DATA.
The communication interface to the reader can be configured in two ways: with a eight line parallel interface (D0:D7) plus DATA_CLK, or with a 4-wire Serial Peripheral Interface (SPI). The SPI interface uses traditional Master Out/Slave In (MOSI), Master In/Slave Out (MISO), Slave Select, and DATA_CLK lines.
These communication modes are mutually exclusive; that is, only one mode can be used at a time in the application.
When the SPI interface is selected, the unused I/O_2, I/O_1, and I/O_0 pins must be hard-wired as shown in Table 6-10. At power up, the TRF7970A samples the status of these three pins and then enters one of the possible SPI modes.
The TRF7970A always behaves as the slave device, and the microcontroller (MCU) behaves as the master device. The MCU initiates all communications with the TRF7970A, and the TRF7970A makes use of the Interrupt Request (IRQ) pin in both parallel and SPI modes to prompt the MCU for servicing attention.
| PIN | PARALLEL | PARALLEL (DIRECT MODE) | SPI WITH SS | SPI WITHOUT SS(5) |
|---|---|---|---|---|
| DATA_ CLK | DATA_CLK | DATA_CLK | DATA_CLK from master | DATA_CLK from master |
| I/O_7 | A/D[7] | Not used | MOSI(1) = data in (reader in) | MOSI(1) = data in (reader in) |
| I/O_6 | A/D[6] | Direct mode, data out (subcarrier or bit stream) | MISO(2) = data out (MCU out) | MISO(2) = data out (MCU out) |
| I/O_5(3) | A/D[5] | Direct mode, strobe – bit clock out | See (3). | See (3). |
| I/O_4 | A/D[4] | Not used | SS – slave select(4) | Not used |
| I/O_3 | A/D[3] | Not used | Not used | Not used |
| I/O_2 | A/D[2] | Not used | At VDD | At VDD |
| I/O_1 | A/D[1] | Not used | At VDD | At VSS |
| I/O_0 | A/D[0] | Not used | At VSS | At VSS |
| IRQ | IRQ interrupt | IRQ interrupt | IRQ interrupt | IRQ interrupt |
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.
| 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 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 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.