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RFID Principles
Table 2. Battery Board Pinouts
Pin
Function
Description
General-purpose digital I/O pin / USCI_A0 transmit data output in UART mode (UART
1
P3.4 / UCA0TXD / UCA0SIMO
communication from MSP430F2274 to PC), slave in/master out in SPI mode
2
GND
Ground reference
Reset or nonmaskable interrupt input
3
RST / SBWTDIO
Spy-Bi-Wire test data input/output during programming and test
Selects test mode for JTAG pins on Port 1. The device protection fuse is connected to
4
TEST / SBWTCK
TEST. Spy-Bi-Wire test clock input during programming and test
5
VCC (3.6 V)
Supply voltage
General-purpose digital I/O pin / USCI_A0 receive data input in UART mode (UART
6
P3.5 / UCA0RXD / UCA0SOMI
communication from 2274 to PC), slave out/master in when in SPI mode
3
RFID Principles
Texas Instruments low-frequency RFID operates at a frequency of 134.2 kHz. A normal RFID system is
completely passive
—
the RFID Reader (the reader is a transceiver but is called only RFID Reader in this
document) sends a command to a RFID transponder, and the transponder answers, normally with its
serial number. The transponder is not connected to a battery; it is completely powered out of the RF field
supplied by the RFID Reader.
The TMS37157 extends this function by a 3 -wire SPI Interface to the MSP430. The TMS37157 is a
semi-active transponder. Its memory can be written through the RF interface (normal transponder
function) without need for a battery or through the SPI interface from a connected microcontroller. It offers
additional functions like a battery check and a battery charge; also it is able to transmit received data from
the RF interface directly to the connected microcontroller.
For ultra-low-power consumption, the TMS37157 offers the possibility to completely switch off the
microcontroller (if powered from VBATI) resulting in an overall power consumption of typically 60 nA. The
eZ430-TMS37157 does not cover this function. The MSP430 is directly connected to the battery.
9
SLAU281B
–
November 2009
–
Revised March 2010
eZ430-TMS37157 Development Tool
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Copyright
©
2009
–
2010, Texas Instruments Incorporated
