The MSC2121A is a modem chip-set that provides full duplex data transmission capability of up to 14400 bits/s conforming to ITU-T Recommendation (V.32 bis, V.22 bis, V.22, and V.21) and Bell Standard (212A and 103J), and also provides facsimile transmission capability conforming to ITU-T Recommendation (V.17, V.33, V.29, and V.27 ter). The MSC2121A supports the function as a facsimile activated by FAX Class 1 Command in EIA Standard, as well as the function to set a modem and to control calls originating and terminating with AT Commands and the function as a data modem including error correction and data compression. So, the use of this chip-set enables easy implementation of terminals that have those functions, which are being widely employed in personal computer communication, as a full-duplex modem of 14400 bits/s and as a facsimile reciever and transmitter. In the MSC2121A, no external program memory will be required because the control program codes are stored in the program memories that a generalpurpose MCV has. General-purpose SRAMs (which are essential) and EEPROMs (which are removable) should be used for external memories. This chip-set comprises the following two LSIs: MSM66507