TCM8002_08 Datasheet, PDF (5/25 Pages) Texas Instruments – DATA PROCESSOR FOR CELLULAR TELEPHONE

TCM8002
DATA PROCESSOR FOR CELLULAR TELEPHONE
SLWS008C − SEPTEMBER 1994 − REVISED JUNE 1996
detailed description
Data communication between the mobile station and the land station in AMPS and TACS systems is achieved
over forward and reverse control channels when a call is not in progress, or in short bursts over the forward and
reverse voice channels when a call is in progress. The TCM8002 device has a receive path that recovers data
from the FOCC (forward control-channel) and FVC (forward voice-channel) formats. The transmit path encodes
and formats data for the RECC (reverse control channel) and RVC (reverse voice channel).
For voice-channel communications, the received SAT is detected and regenerated for transmission.
Communication with the microcontroller/microprocessor in the telephone is through a serial interface. The
TCM8002 also provides interrupts to alert the processor to the occurrence of specific events. The receiver is
made up of the Data Recovery, Majority Voting, BCH (Bose-Chaudhuri-Hocquenghem) Decoder, RX Buffer,
Arbitration Logic, and RX Control blocks. The SAT Detector/Regenerator is used during FVC reception and RVC
transmission.
The transmit path consists of the TX Buffer and TX Encoder blocks. A serial microprocessor interface and the
interrupt logic are also provided. Four ancillary functions are included:
• TCM8010 interface
• Watchdog Timer
• Counter/Timer
• twenty programmable digital bidirectional I/O lines (eight of the output terminals can be reconfigured as
processor output ports)
clock divider
The clock signal for the TCM8002 is supplied in two ways:
• A crystal can be connected to XTAL1 and XTAL2.
• A clock signal from another source can be connected to XTAL1.
When a crystal is used, a resistor (typical value 1 MΩ) should be connected between XTAL1 and XTAL2 to
provide a bias for the oscillator. The crystal frequency must be 2.56 MHz, 5.12 MHz, 7.68 MHz, or 10.24 MHz.
If an external clock signal is connected, it must be at one of these crystal frequencies or one of two additional
frequencies: 15.36 MHz or 20.48 MHz.
The clock frequency defaults to 2.56 MHz when the TCM8002 is reset. The clock-divider circuit provides a
2.56-MHz clock for internal use and must be configured according to the selected crystal or external clock
frequency. Control word 2, bits 5 and 6, and control word 4, bit 1, are used to configure the clock divider. The
output from the clock-divider circuit is provided at CLKOUT and is always 2.56 MHz. This can be used to clock
the TCM8010 advanced audio processor.
The bit rate of the transmitted Manchester-encoded data, the signaling-tone frequency, and the accuracy of the
SAT measurement are all determined by the crystal or external clock. The AMPS and TACS system
requirements both specify a maximum transmitted bit frequency error of ± 100 ppm; therefore, over the
operating temperature range of the phone, the crystal or clock frequency error must be no more than ± 100 ppm.
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