Programmable Four-Channel Communications Controller

The CD2481 is a four-channel synchronous/asynchronous communications controller specifically designed to reduce host-system processing overhead and increase efficiency in a wide variety of communications applications. A special member of the CD24X1 family, the device allows easy field upgrades and enhancement with an on-chip 8K-word microcode store for downloaded control code. The CD2481 is packaged in a 100-pin MQFP package that offers 10 data/clock/modem pins per channel. The device has four fully independent serial channels to support standard asynchronous, PPP, MNP4, SLIP, bit-synchronous (HDLC), and byte-synchronous (bisync, X.21) protocols. The device is non-functional until the microcode is downloaded; only a small boot ROM with code to perform device initialization is included.

FEATUREs
• Four full-duplex multi-protocol channels, each running up to 230.4 kbps (with 60-MHz clock)
• Microcode downloadable to on-chip storage supports various asynchronous and synchronous protocols on all channels
• 32-bit address, 16-bit data, double-buffered DMA (direct memory access) controller for each transmitter and receiver; two independent bit-rate generators per channel for transmit and receive
• On-chip NRZ (nonreturn-to-zero), NRZI (nonreturn-to-zero inverted), and Manchester data encoding and decoding
• DPLL (digital phase locked loop) on each receiver
• Two independent timers per channel