DA7838.002

20 September, 2000

5 (9)

)81&7,216

u 7LPLQJ VHOHFWLRQ

The MAS7838 requires clock signals in order to function

properly. The synchronous data transfer always

requires the TXC clock. The clock is used internally for:

-shifting data out from the TX buffer (to pin TDO)

-shifting data into the RX buffer (via pin RDI)

-detection of the bit rate in order to adjust the internal

baud rate generator (only if TSL = 1)

The asynchronous data transfer (pins TDI, TDO) is

accomplished by generating an internal timing signal for

the asychronous circuits. This internal timing signal

(16T) is 16 times the TXC bit rate in order to sample the

asynchronous data stream (TDI) at the proper speed.

$33/,&$7,21 ,1)250$7,21

u 6\QFKURQRXV PRGHP ZLWK DV\QFKURQRXV LQWHUIDFH

The MAS7838 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.

16 x TXC

TXC

Timing Circuits

MAS 7838

EXTERNALLY GENERATED 16T CLOCK

MAS9138

TXD

RXD

TDI

RDO

INTERFACE

RS232C

MODEM CIRCUITS

PHONE LINE

TDO

TXC

RDI

RXC