CMX989 Datasheet, PDF (9/31 Pages) CML Microcircuits – CDPD MAC and Data Pump Processor

CDPD MAC and Data Pump Processor
CMX989
1.5.2 Detailed Function List
1.5.2.1 Separate 141-byte Tx and Rx data buffers, organized as byte-wide CDPD frame FIFOs
• Large enough to hold an entire maximum length (136-byte) CDPD frame
• Decouples host CPU and CDPD airlink to provide opportunities for CPU powersave and relaxed
service routine timing requirements
• Rx management automatically flushes erroneous frames and resynchronises Rx buffer on valid
frame synchronization
• Empty/full status
• Tx frames are written byte-by-byte style and separated from subsequent frames by writing to an
end of frame marker
• Rx frames are read byte-by-byte with each frame boundary indicated by an IRQ and related
status
• Read and write status/IRQ handshake paces each byte transferred to and from FIFOs
1.5.2.2 Encapsulates/de-encapsulates CDPD frames to/from over-air signal systems
• Completed Reed-Solomon block encode and decode with automated ‘fill’ function for partially
filled
Tx blocks
• Colour Code automatically extracted from Rx stream and inserted into Tx stream
• Pseudo-random number scrambling
• Status flags available for reading or to IRQ on: number of errors corrected in Rx Reed-Solomon
block, number errors in forward sync word, Rx busy/idle, Rx Colour Code, MDBS decode, etc.
1.5.2.3 19.2kbps (BT = 0.5) GMSK modem data pump
• Discriminator Rx interface
• Rx frame synchronisation recognizer triggers internal ‘upper layer’ processing
• Intelligent Tx emission triggering:
• Tx emission start is synchronized to Rx Busy/Idle flag timing
• Tx FIFO may be loaded before issuing an emission request or emission request may be
issued first and remains pending until Tx FIFO is loaded with enough data to generate a
Reed-Solomon block
• Host µController and TXRFEN signals available to enable ramp-up and ramp-down control
of external RF power amplifier stage
• Dual, independent gain controlled Tx outputs for low frequency response transmit VCO
architecture
© 2001 Consumer Microcircuits Limited
9
D/989/2