xr16c2550ip Exar Corporation, xr16c2550ip Datasheet - Page 9

• Manufacturer Part Number: xr16c2550ip
• Description: Dual Uart With 16-byte Transmit And Receive Fifos
• Manufacturer: Exar Corporation

xr
REV. 1.0.1
The 2550 includes an on-chip oscillator (XTAL1 and XTAL2) to produce a clock for both UART sections in the
device. The CPU data bus does not require this clock for bus operation. The crystal oscillator provides a
system clock to the Baud Rate Generators (BRG) section found in each of the UART. XTAL1 is the input to the
oscillator or external clock buffer input with XTAL2 pin being the output.
Generator” on page 9.
The on-chip oscillator is designed to use an industry standard microprocessor crystal (parallel resonant,
fundamental frequency with 10-22 pF capacitance load, ESR of 20-120 ohms and 100ppm frequency
tolerance) connected externally between the XTAL1 and XTAL2 pins (see
1 MΩ resistor across it. Alternatively, an external clock can be connected to the XTAL1 pin to clock the internal
baud rate generator for standard or custom rates. Typical oscillator connections are shown in
further reading on oscillator circuit please see application note DAN108 on EXAR’s web site.
A single baud rate generator is provided for the transmitter and receiver, allowing independent TX/RX channel
control. The programmable Baud Rate Generator is capable of operating with a crystal frequency of up to 24
MHz. However, with an external clock input on XTAL1 pin and a 2K ohms pull-up resistor on XTAL2 pin (as
shown in
5.0V.
2.7
2.8
Crystal Oscillator or External Clock Input
Programmable Baud Rate Generator
Figure
5) it can extend its operation up to 64 MHz (4Mbps serial data rate) at room temperature and
F
IGURE
22-47 pF
XTAL1
4. T
C1
YPICAL OSCILLATOR CONNECTIONS
500 Κ Ω − 1 Μ Ω
R2
22-47 pF
9
XTAL2
C2
Y1
1.8432 MHz
(Optional)
2.97V TO 5.5V DUART WITH 16-BYTE FIFO
0-120
24 MHz
R1
to
Ω
Figure
See “Programmable Baud Rate
4), with an external 500kΩ to
XR16C2550
Figure
4. For