Datasheet
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4/12/2010
#26217
With more people using the Internet, new demands have
been placed on computer serial ports. Many PC serial ports aren’t
equipped to handle the level of buffering required for newer data
rates. But advanced UARTs—such as the 16550, 16650, 16750,
and 16850—go a long way toward satisfying the requirements.
I/O addresses and IRQs
All the UARTs in the PCI cards are buffered, so the CPU
is not constantly interrupted to process data.
The adapter is automatically assigned I/O addresses and IRQs
by the motherboard BIOS. Only the IRQ address can be modified
by the user.
16550 UART
Used in the IC133C-R2 and IC141C-R2, the 16550 features
a 16-byte input and output First-In, First-Out (FIFO) buffer that
holds charac ters for the transmitter and recei ver. The FIFO enables
you to obtain higher data rates while reducing the frequency of
processor interrupts. It supports sustained data rates up to 115.2
kbps or bursts of data up to 460.8 kbps.
16554 UART
Used in the IC142C, two 16554 UARTs contain four 16550
UARTs, each with a 16-byte FIFO buffer.
16650 UART
Used in the IC140C-R2, the 16650 UART features a 32-byte
FIFO buffer and can handle sus tained data rates up to 460.8 kbps.
But you must use the appropriate line drivers and receivers and
be able to optimize the other factors that affect performance
(such as CPU, number of ports, cable length and quality, and
electrical interface).
16750 UART
Used in the IC143C-R2, the 16750 has a 64-byte FIFO buffer.
It also features sustained baud rates of 460.8 kbps but delivers
better performance because of its larger buffer.
16850 UART
Used in the IC970C-LP, IC971C, IC975C-LP, ICR975C-LP,
IC972C-R2, IC187C-LP, IC973C–IC974C, IC187C, and IC189C,
the 16850 UART has a 128-byte FIFO buffer for each port.
The 16850 UART features FIFO UARTs that enhance communi-
cations. They help you avoid the many I/O problems—like data
overruns or underruns—that occur in a multitasking environment
when the UART buffering isn’t large enough to handle the
incoming data. These, of course, can interrupt performance
and affect your communications.
The 16850 chip also supports an isochronous scheme, which
is asynchronous framing with the addition of clock signal. This
scheme allows for much higher data rates and the use of a digital
line (ISDN, T1) where a clock is supplied for data multiplexing.
And you can get high-speed communications with a simple
communications interface that responds to standard communi-
cation calls.
16854 UART
Used in the IC188C-R2, IC190C-R2, and IC1600C, the two
16854 UARTs contain four 16850 UARTs, each with a 128-byte
FIFO buffer.
16C864 UART
Used in the IC978C, the two 16C864 UARTs contain four
16860 UARTs. Each UART has a 128-byte FIFO buffer.
Technically Speaking