ST16C550(2003) View Datasheet(PDF) - Exar Corporation
Part Name
Description
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ST16C550 Datasheet PDF : 35 Pages
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ST16C550
SYMBOL DESCRIPTION
Symbol
-DDIS
-OP1
RESET
RCLK
-OP2
VCC
XTAL1
XTAL2
-CD
Pin
Signal
40 44 48 type
Pin Description
23
26
22
O Drive Disable. This pin goes to a logic 0 when the external
CPU is reading data from the ST16C550. This signal can be
used to disable external transceivers or other logic func-
tions.
34
38
34
O Output-1 (User Defined) - See bit-2 of modem control
register (MCR bit-2).
35 39 35
I Reset. (active high) - A logic 1 on this pin will reset the
internal registers and all the outputs. The UART transmitter
output and the receiver input will be disabled during reset
time. (See ST16C550 External Reset Conditions for initial-
ization details.)
9
10
5
I Receive Clock Input. This pin is used as external 16X clock
input to the receiver section. External connection to -
Baudout pin is required in order to utilize the internal baud
rate generator.
31
35
31
O Output-2 (User Defined). This pin provides the user a
general purpose output. See bit-3 modem control register
(MCR bit-3).
40 44
42 Pwr Power Supply Input.
16 18 14
I 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 MΩ 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).
17
19
15
O Output of the Crystal Oscillator or Buffered Clock - (See also
XTAL1). Crystal oscillator output or buffered clock output.
38 42
40
I Carrier Detect (active low) - A logic 0 on this pin indicates
that a carrier has been detected by the modem.
Rev. 4.30
6
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