XR16C850CM EXAR [Exar Corporation], XR16C850CM Datasheet - Page 13

• Manufacturer Part Number: XR16C850CM
• Description: 2.97V TO 5.5V UART WITH 128-BYTE FIFO
• Manufacturer: EXAR [Exar Corporation]

xr
REV. 2.3.1
The output function of interrupt outputs change according to the operating bus type. During the Intel Bus Mode,
the INT output will always be active high and MCR bit-3 will have no effect on the INT output pin. In the PC
Mode, the IRQ outputs are in three-state mode unless MCR bit-3 and S3 are both a logic 1.
summarizes its behavior in Intel and PC mode of operation.
The 850 includes an on-chip oscillator (XTAL1 and XTAL2). The crystal oscillator provides the system clock to
the Baud Rate Generators (BRG) in the UART. XTAL1 is the input to the oscillator or external clock buffer input
with XTAL2 pin being the output. For programming details, see
Generator” on page
Intel bus mode, the BAUDCLK pin must be connected to the RCLK pin external to the UART.
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 baud rate generator for standard or custom rates.
Typically, the oscillator connections are shown in
application note DAN108 on EXAR’s web site.
2.9
2.10
Interrupts
Crystal Oscillator or External Clock
14. To use the same clock for the receiver as used with the transmiter of the UART in the
Intel
PC
M
B
ODE
US
F
T
ABLE
IGURE
B
MCR
22-47pF
XTAL1
3: I
IT
X
0
0
1
1
7. T
C1
-3
NTERRUPT
YPICAL OSCILLATOR CONNECTIONS
(PC M
Figure
O
500K - 1M
S3
NLY
X
0
1
0
1
R2
13
ODE
22-47pF
XTAL2
)
O
C2
Y1
UTPUT
7. For further reading on oscillator circuit please see
Active High
Three-State
Three-State
Three-State
Active High
I
NTERRUPT
1.8432 MHz
(Optional)
2.97V TO 5.5V UART WITH 128-BYTE FIFO
F
24 MHz
(INT
0-120
UNCTIONS
R1
“Section 2.11, Programmable Baud Rate
to
OR
O
IRQ)
UTPUT
Figure
7). Alternatively, an external
XR16C850
Table 3