xr16l784iv Exar Corporation, xr16l784iv Datasheet - Page 7

• Manufacturer Part Number: xr16l784iv
• Description: High Performance 2.97v To 5.5v Quad Uart
• Manufacturer: Exar Corporation

xr
REV. 1.2.2
The INT# interrupt output changes according to the operating mode and enhanced features setup.
and 3
The 784 includes an on-chip oscillator (XTAL1 and XTAL2). The crystal oscillator provides the system clock to
the Baud Rate Generators (BRG) in each of the 8 UARTs, the 16-bit general purpose timer/counter and
internal logics. XTAL1 is the input to the oscillator or external clock buffer input with XTAL2 pin being the
output. For programming details, see
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
clock can be connected to the XTAL1 pin to clock the internal 8 baud rate generators for standard or custom
rates. Typically, the oscillator connections are shown in
see application note DAN108 on EXAR’s web site.
2.4
2.5
INT# Pin
INT# Pin
summarize the operating behavior for the transmitter and receiver.
INT# Ouput
CRYSTAL OSCILLATOR / BUFFER
INT# Pin
Auto RS485
Mode
YES
NO
HIGH = no data
LOW = 1 byte
F
IGURE
HIGH = a byte in THR
LOW = THR empty
HIGH = a byte in THR
LOW = transmitter empty
T
ABLE
T
(FIFO D
ABLE
FCR B
(FIFO D
3. T
FCR B
“Section 2.6, Programmable Baud Rate Generator” on page
2: INT# P
3: INT# P
YPICAL OSCILLATOR CONNECTIONS
IT
ISABLED
-0 = 0
22-47pF
IT
ISABLED
XTAL1
-0 = 0
C1
R=300K to 400K
IN
)
IN
)
O
14.7456
O
PERATION FOR
MHz
PERATION
7
Figure
HIGH = FIFO above trigger level
LOW = FIFO below trigger level or FIFO empty
HIGH = FIFO above trigger level
LOW = FIFO below trigger level or transmitter empty
HIGH PERFORMANCE 2.97V TO 5.5V QUAD UART
HIGH = FIFO below trigger level
LOW = FIFO above trigger level
22-47pF
XTAL2
C2
3. For further reading on oscillator circuit please
F
OR
T
RANSMITTER
R
(FIFO E
ECEIVER
FCR B
Figure
(FIFO E
FCR B
IT
NABLED
-0 = 1
3). Alternatively, an external
IT
NABLED
)
-0 = 1
)
XR16L784
8.
Table 2