xr16l2550im Exar Corporation, xr16l2550im Datasheet - Page 9

• Manufacturer Part Number: xr16l2550im
• Description: Industry Smallest Package Uart With 2.25v To 5.5v Operation
• Manufacturer: Exar Corporation

REV. 1.1.2
The L2550 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. For programming details, see
“Programmable Baud Rate Generator.”
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 100 ppm frequency
tolerance) connected externally between the XTAL1 and XTAL2 pins (see
to 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
For further reading on oscillator circuit please see application note DAN108 on EXAR’s web site.
2.9
INTA/B Pin
INTA/B Pin
Crystal Oscillator or External Clock Input
0 = a byte in THR
1 = THR empty
0 = no data
1 = 1 byte
T
(FIFO D
(FIFO D
ABLE
FCR B
T
FCR B
ABLE
3: INTA
IT
ISABLED
IT
ISABLED
-0 = 0
F
4: INTA
-0 = 0
IGURE
)
22-47 pF
AND
)
XTAL1
4. T
AND
C1
INTB P
YPICAL OSCILLATOR CONNECTIONS
INTB P
500 Κ Ω − 1 Μ Ω
0 = at least 1 byte in FIFO
1 = FIFO empty
0 = FIFO below trigger level
1 = FIFO above trigger level
INS
R2
22-47 pF
IN
9
XTAL2
O
C2
O
Y1
PERATION FOR
PERATION
LOW VOLTAGE DUART WITH 16-BYTE FIFO
1.8432 MHz
(Optional)
0-120
24 MHz
R1
to
F
Ω
OR
T
(FIFO E
(FIFO E
FCR B
FCR B
RANSMITTER
R
ECEIVER
Figure
IT
IT
NABLED
NABLED
-0 = 1
-0 = 1
4), with an external 500 kΩ
)
)
XR16L2550
Figure
4.