ST16C450
SYMBOL DESCRIPTION
Symbol
Pin
44
Signal
type
Pin Description
40
48
-RI
39
43
41
I
RingIndicator(activelow)-Alogic0onthispinindicatesthe
modem has received a ringing signal from the telephone
line. A logic 1 transition on this input pin will generate an
interrupt.
-RTS
32
36
32
O
Request to Send (active low) - A logic 0 on the -RTS pin
indicatesthetransmitterhasdatareadyandwaitingtosend.
Writing a logic 1 in the modem control register (MCR bit-1)
will set this pin to a logic 0 indicating data is available. After
a reset this pin will be set to a logic 1. This pin has no effect
on the UART’s transmit or receive operation.
RX
TX
10
11
11
13
7
8
I
Receive Data - This pin provides the serial receive data
inputtotheST16C450. TheRXsignalwillbealogic1during
reset, idle (no data). During the local loop-back mode, the
RX input pin is disabled and TX data is internally connected
to the UART RX Input, internally, see figure 12.
O
Transmit Data - This pin provides the serial transmit data
from the ST16C450, the TX signal will be a logic 1 during
reset, idle (no data). During the local loop-back mode, the
TX input pin is disabled and TX data is internally connected
to the UART RX Input, see figure 12.
GENERAL DESCRIPTION
provide all these functions is fairly complex especially
whenmanufacturedonasingleintegratedsiliconchip.
The ST16C450 represents such an integration with
greatlyenhancedfeatures.TheST16C450isfabricated
with an advanced CMOS process. The ST16C450 is
designedtoworkwithhighspeedmodemsandshared
networkenvironments.
The ST16C450 provides serial asynchronous receive
data synchronization, parallel-to-serial and serial-to-
parallel data conversions for both the transmitter and
receiver sections. These functions are necessary for
convertingtheserialdatastreamintoparalleldatathat
is required with digital data systems. Synchronization
for the serial data stream is accomplished by adding
start and stops bits to the transmit data to form a data
character (character orientated protocol). Data integ-
rity is insured by attaching a parity bit to the data
character. The parity bit is checked by the receiver for
any transmission bit errors. The electronic circuitry to
The ST16C450 is capable of operation to 1.5Mbps
with a 24 MHz crystal or external clock input.
With a crystal of 14.7464 MHz and through a software
option, the user can select data rates up to 460.8Kbps
or 921.6Kbps.
Rev.4.20
7
EXAR [ EXAR CORPORATION ]
