Trf7970A Reader System Using Spi With Ss Mode - Texas Instruments TRF7970A Instruction Manual

TRF7970A
SLOS743K – AUGUST 2011 – REVISED APRIL 2014
7.2

TRF7970A Reader System Using SPI With SS Mode

7.2.1 General Application Considerations
Figure 7-2 shows the TRF7970A application schematic optimized for both ISO15693 and ISO14443
systems using the Serial Port Interface (SPI). Short SPI lines, proper isolation of radio frequency lines,
and a proper ground area are essential to avoid interference. The recommended clock frequency on the
DATA_CLK line is 2 MHz.
Figure 7-2 shows matching to a 50-Ω port, which allows connecting to a properly matched 50-Ω antenna
circuit or RF measurement equipment (for example, a spectrum analyzer or power meter).
An MSP430F2370 (32KB Flash, 2KB RAM) is shown in
on application requirements and coding style. If only one ISO protocol or a limited command set of a
protocol needs to be supported, MCU Flash and RAM requirements can be significantly reduced and user
should be aware that recursive inventory and anticollision commands require more RAM than single
slotted operations. For example, current reference firmware for ISO15693 (with host interface) is
approximately 8KB, using 512B RAM and for all supported protocols (also with same host interface) the
reference firmware is approximately 12KB and uses a minimum of 1KB RAM. An MCU capable of running
its GPIOs at 13.56 MHz is required for Direct Mode 0 operations.
76 Application Schematic and Layout Considerations
Figure
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7-2. Minimum MCU requirements depend
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