Intermec 869 RFID Reader, Service Instructions Manual

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Theory of Operation Chapter
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2
14 869 RFID Reader Service Instruction Manual
Memory
This buffer is the origin of the search function and where all RFID tag
reads are initially sorted for redundant data. The buffer is sized to hold up
to 100 unique tag serial numbers to match incoming values, or 100
unique tag serial numbers used to match multiple reads of the same tag.
Flash
An AMD 1Mx16-Bit Flash memory (AM29LV16BB) provides space for
the program memory. It is a relatively slow (120 nsec) part and thus is not
used for program execution. At power-up, the program in Flash is copied
to internal RAM (6.25ns) and/or external SDRAM (7 ns) and executed
from there.
SDRAM
The SDRAM memory used is a Micron (MT48LC2M32) 64Mbit
(2Mx32bit) SDRAM memory that is high speed (upto 143 MHz) and low
cost. The memory can be used for program and data storage. SimultaĆ
neous program and data storage is possible do to the DSP using a unified
memory map.
SPI Serial Interface
There is an 8Kbit (1Kx8bit) SPI type MicroChip 25C080 EEPROM, used
for country code and radio parameter settings.
LATTICE ANTI-ALIASING FILTERS AND AMPLIFIERS
The I and Q receive channels each have a high gain wide band differential
amplifier followed by programmable differential amplifier/filter, a Lattice
ISPPAC80. The filters are currently programmed as low pass with a 3dB
knee at 200 kHz for use as the anti-aliasing filters before the A/D. The
filters can be dynamically programmed by the DSP.
D/A CONVERTER
A two channel, 1MSPS D/A (AD7303), provides transmit modulation on
one channel and transmit power control on the other. The D/A is conĆ
nected to the same McBSP as the EEPROM, and receiver anti-aliasing filĆ
ters. The D/A can support up to 25 samples/bit, given a data rate of 40
KHz.
RECONSTRUCTION FILTERS
Each D/A channel has a reconstruction filter on its output to filter out the D/A
sample frequency. These are Sallen-Key low pass filters with a 3dB knee of 1
MHz for the modulation filter and 100 KHz for the power control filter.