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DA9138.005

12 April, 2006

APPLICATION INFORMATION

Synchronous modem with asynchronous interface

The MAS9138 is intended for applications where an asynchronous and synchronous data source must be linked

together. A typical case appears in a data modem where the terminal interface of the modem has been specified to

be asynchronous but the modem data pump operates in a synchronous fashion.

MAS9138

TXD

RXD

TDI

RDO

INTERFACE

RS232C

MODEM CIRCUITS

PHONE LINE

TDO

TXC

RDI

RXC

Synchronous serial interface with uP interface

Another application is a synchronous serial interface for uP which uses UART as a data source. The concept is

illustrated below.

MAS9138

TTL/V.28

UART

uP-INTERFACE

RDI

TDO

TxD

RxD

RxC

TxC

RS-232-C

V.24