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ST16C452CJ68

DUAL UART WITH PARALLEL PRINTER PORT

Exar Corporation 

ST16C452/452PS

Table 4, INTERNAL REGISTER DECODE

A2 A1 A0

READ MODE

WRITE MODE

General Register Set (THR/RHR, IER/ISR, MCR/MSR, LCR/LSR, SPR): Note 1*

0

0

0

0

0

1

0

1

0

0

1

1

1

0

0

1

0

1

1

1

0

1

1

1

Receive Holding Register

Interrupt Status Register

Line Status Register

Modem Status Register

Scratchpad Register

Transmit Holding Register

Interrupt Enable Register

Line Control Register

Modem Control Register

Scratchpad Register

Baud Rate Register Set (DLL/DLM): Note *2

0

0

0

0

0

1

LSB of Divisor Latch

MSB of Divisor Latch

LSB of Divisor Latch

MSB of Divisor Latch

Printer Port Set (PR/SR/IOSEL/COM/CON): Note *3

X

0

0

X

0

1

X

1

0

PORT REGISTER

STATUS REGISTER

COMMAND REGISTER

PORT REGISTER

I/O SELECT REGISTER

CONTROL REGISTER

Note 1* The General Register set is accessible only when CS A or CS B is a logic 0.

Note 2* The Baud Rate register set is accessible only when CS A or CS B is a logic 0 and LCR bit-7 is a logic 1.

Note 3*: Printer Port Register set is accessible only when -CSP is a logic 0 in conjunction with the states of the

interface signal BIDEN and Printer Control Register bit-5 or IOSEL register.

Programmable Baud Rate Generator

The 452/452PS supports high speed modem technolo-

gies that have increased input data rates by employing

data compression schemes. For example a 33.6Kbps

modem that employs data compression may require a

115.2Kbps input data rate. A 128.0Kbps ISDN modem

that supports data compression may need an input data

rate of 460.8Kbps. The 452/452PS can support a

standard data rate of 921.6Kbps.

Single baud rate generator is provided for the transmitter

and receiver, allowing independent TX/RX channel con-

trol. The programmable Baud Rate Generator is capable

of accepting an input clock up to 24 MHz, as required

for supporting a 1.5Mbps data rate. The 452/452PS

requires that an external clock source be connected to

the CLK input pin to clock the internal baud rate

generator for standard or custom rates. (see Baud Rate

Generator Programming below).

Rev. 3.20

9

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