A full duplex 1200/300 bit/s single-chip CMOS model

The design of a Bell 212A (AT&T) compatible single-chip modem is described, and measured results are presented. The IC(Fairchild /spl mu/A212A) contains all signal-processing functions and supports all operating modes, including test modes and selection of either 1200 bit/s QPSK or 300 bit/s FSK operation. The modem offers such features as a coherent digital receiver, call-progress toner monitoring, 8-11 bit character lengths for asynchronous operation, and on-chip handshaking for the remote loopback test mode. Only connect and disconnect sequences are user-provided typically by a (generic) microcontroller.