ST16C454(1994) 查看數據表（PDF） - Exar Corporation
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ST16C454 Datasheet PDF : 30 Pages
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ST16C454/68C454
GENERAL DESCRIPTION
The 454 provides serial asynchronous receive data
synchronization, parallel-to-serial and serial-to-paral-
lel data conversions for both the transmitter and
receiver sections. These functions are necessary for
converting the serial data stream into parallel data that
is required with digital data systems. Synchronization
for the serial data stream is accomplished by adding
start and stops bits to the transmit data to form a data
character (character orientated protocol). Data integ-
rity is insured by attaching a parity bit to the data
character. The parity bit is checked by the receiver for
any transmission bit errors. The electronic circuitry to
provide all these functions is fairly complex especially
when manufactured on a single integrated silicon
chip. The ST16C454 represents such an integration
with greatly enhanced features. The 454 is fabricated
with an advanced CMOS process to achieve low drain
power and high speed requirements.
The 454 combines the package interface modes of the
ST16C454 and ST68C454 series on a single inte-
grated chip. The 16 mode interface is designed to
operate with the Intel type of microprocessor bus while
the 68 mode is intended to operate with Motorola, and
other popular microprocessors.
The 454 is capable of operation to 1.5Mbps with a 24
MHz crystal or external clock input. With a crystal of
14.7464 MHz, the user can select data rates up to
921.6Kbps.
The rich feature set of the 454 is available through
internal registers. Selectable TX and RX baud rates,
modem interface controls. In the 16 mode INTSEL
and MCR bit-3 can be configured to provide a software
controlled or continuous interrupt capability.
FUNCTIONAL DESCRIPTIONS
Interface Options
Two user interface modes are selectable for the 454
package. These interface modes are designated as
the 16 mode and the 68 mode. This nomenclature
corresponds to the early ST16C454 and ST68C454
package interfaces respectively.
The 16 Mode Interface
The 16 mode configures the package interface pins for
connection as a standard 16 series (Intel) device and
operates similar to the standard CPU interface avail-
able on the ST16C454. In the 16 mode (pin 16/-68
logic 1) each UART is selected with individual chip
select (-CSx) pins as shown in Table 2 below.
Table 2, SERIAL PORT CHANNEL SELECTION
GUIDE, 16 MODE INTERFACE
-CSA -CSB -CSC -CSD
1
1
1
1
0
1
1
1
1
0
1
1
1
1
0
1
1
1
1
0
UART
CHANNEL
None
A
B
C
D
The 68 Mode Interface
The 68 mode configures the package interface pins for
connection with Motorola, and other popular micro-
processor bus types. The interface operates similar to
the ST68C454. In this mode the 454 decodes two
additional addresses, A3-A4 to select one of the four
UART ports. The A3-A4 address decode function is
used only when in the 68 mode (16/-68 logic 0), and is
shown in Table 3 below.
Table 3, SERIAL PORT CHANNEL SELECTION
GUIDE, 68 MODE INTERFACE
-CS A4 A3
1 N/A N/A
0
0
0
0
0
1
0
1
0
0
1
1
UART
CHANNEL
None
A
B
C
D
Rev. 3.20
9
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