Spread-
Spectrum
Signal
Processor
Integrated
Circuit
Preliminary
Features
•
Two Independent PN (Pseudo-Random Noise) Generators
•
Programmable R7 (128) to R13 (8,192) PN Sequence Lengths
•
Programmable Tau-Dither Amplitude
•
Programmable PN Phase Adjustment to 1/16 Chip
•
Correlation Acquisition Interface
•
Programming Register Control
•
Microcontroller Compatible Bus Interface
•
Patent-Pending Frequency Diversity
•
Low Speed Link Data Path for Supervisory and Setup Functions
Description
The AT48802 Spread-Spectrum Signal Processor (SSSP) chip from Atmel handles
all PN code generation, synchronization, and handshaking required for either station
(handset or base station) of a time division duplex direct sequence spread-spectrum
cordless telephone. The AT48802 supports RF spreading and despreading for the
best rejection of interference. In conjunction with a single-chip microcontroller, the
circuit performs the following functions:
• Generates a pseudo-random sequence for spreading the transmitted signal.
• Generates a pseudo-random sequence for despreading in the receiver.
• Generates a sliding phase PN for acquiring synchronization with an incoming
signal.
• Controls receive signal strength measurement timing for correlation peak
detection.
• Operates a tau-dither tracking loop, with adaptive threshold, to maintain
synchronization with the incoming signal.
• Controls transmit keying antenna switching for time-division duplexing.
(continued)
0624A
64 Lead PQFP
Pin Configuration
AT48802
2-1