User's Manual

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6.4.3 Debug/Personality Module Support
The reader board can be programmed and/or debugged from a Microchip ICD 3 module via J15. The connector is also compatible with
Manitowoc’s personality module for applications that desire external flash memory.
6.4.4 Reset
The reader board can reset by momentarily grounding (~100ms) J15-1 pin. This will cause the entire board to reset and restart the
initialization routine.
6.5 Communication Peripherals
6.5.1 MODBUS Interface
The reader board translates UART signals from the microcontroller to RS-485 levels using ST485EBDR transceivers. Both a peripheral
bus (P-BUS) and a communication bus (C-BUS) are provided. Both buses are terminated using the Manitowoc scheme shown in
Appendix A, filtered and routed to J14.
6.5.2 SPI Interface
The reader board utilizes SPI protocol (and is so configured) for communications from the microcontroller and the RFID transceiver.
The signals RFID_CS, MISO, MOSI, and SPI_CLOCK are used.
The SPI bus runs at 2MHz.
The reader board also has the capability to communicate to a PM via the same SPI bus using the PM_CS signal on the J15 connector.
6.6 RFID Transceiver
The reader board utilizes TI’s TRF7970A multiprotocol 13.56MHz RFID and NFC transceiver IC. It provides a built-in data framing engine
for several protocols including ISO15693, ISO18000-3, ISO14443A/B, and FeliCa as well as the integrated analog front end. It is also
configured for single-ended output (signal ground referenced) which facilitates multiplexing applications.
The power supply for the transceiver can be run from 5V2 or 3V3 voltage rail by populating either R1(5V2) OR R2(3V3) zero ohm
resistor.
The transceiver runs from a 13.56MHz crystal, which in turn supplies SYS_CLOCK to the microcontroller at 13.56MHz, 6.78MHz, or
3.39MHz depending on software configuration.
An impedance-matching circuit from the 4 Ohm (TX output) to 50 Ohm impedance designed for 50 Ohm tuned antennas and cabling
systems is provided on board and is shown below:
The transceiver is enabled via RFID_EN (active-high) from the microcontroller. Anytime a new tag is detected the transceiver will drive
the RFID_IRQ low and hold it until the package is read by the microcontroller.
The signals RFID_ASK and RFID_MOD are provided to microprocessor for applications that desire to use the RFID transceiver in
DIRECT_MODE. Although most applications will want to take advantage of the data format engine included in the chip.