ST16C450 Exar Corporation, ST16C450 Datasheet - Page 6

• Manufacturer Part Number: ST16C450
• Description: UNIVERSAL ASYNCHRONOUS RECEIVER/TRANSMITTER (UART)
• Manufacturer: Exar Corporation

ST16C450
SYMBOL DESCRIPTION
-OP2
VCC
XTAL1
XTAL2
-CD
-CTS
-DSR
-DTR
Symbol
Rev. 4.20
40
40
16
17
38
36
37
33
31
Pin
40
37
44
35
44
18
19
42
41
48
31
14
15
38
39
33
42
40
Signal
type
Pwr
O
O
O
I
I
I
I
Output-2 (User Defined). This pin provides the user a general
purpose output. See bit-3 modem control register (MCR bit-
3).
Power Supply Input.
Crystal or External Clock Input - Functions as a crystal input
or as an external clock input. A crystal can be connected
between this pin and XTAL2 to form an internal oscillator
circuit. An external 1 MW resistor is required between the
XTAL1 and XTAL2 pins (see figure 3). Alternatively, an
external clock can be connected to this pin to provide
custom data rates (Programming Baud Rate Generator
section).
Output of the Crystal Oscillator or Buffered Clock - (See also
XTAL1). Crystal oscillator output or buffered clock output.
Carrier Detect (active low) - A logic 0 on this pin indicates
that a carrier has been detected by the modem.
Clear to Send (active low) - A logic 0 on the -CTS pin
indicates the modem or data set is ready to accept transmit
data from the ST16C450. Status can be tested by reading
MSR bit-4. This pin has no effect on the UART’s transmit or
receive operation.
Data Set Ready (active low) - A logic 0 on this pin indicates
the modem or data set is powered-on and is ready for data
exchange with the UART. This pin has no effect on the
UART’s transmit or receive operation.
Data Terminal Ready (active low) - A logic 0 on this pin
indicates that the ST16C450 is powered-on and ready. This
pin can be controlled via the modem control register.
Writing a logic 1 to MCR bit-0 will set the -DTR output to
logic 0, enabling the modem. This pin will be a logic 1 after
writing a logic 0 to MCR bit-0, or after a reset. This pin has
no effect on the UART’s transmit or receive operation.
6
Pin Description