ST16C454(1994) 查看數據表（PDF） - Exar Corporation

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ST16C454
(Rev.:1994)

QUAD UNIVERSAL ASYNCHRONOUS RECEIVER/TRANSMITTER (UART)

Exar Corporation 

ST16C454/68C454

Internal Registers

The 454 provides 12 internal registers for monitoring

and control. These resisters are shown in Table 4

below. These registers are similar to those already

available in the standard 16C450. These registers

function as data holding registers (THR/RHR), inter-

rupt status and control registers (IER/ISR), line status

and control registers (LCR/LSR), modem status and

control registers (MCR/MSR), programmable data

rate (clock) control registers (DLL/DLM), and a user

assessable scratchpad register (SPR). Register func-

tions are more fully described in the following para-

graphs.

Table 4, INTERNAL REGISTER DECODE

A2 A1 A0

READ MODE

WRITE MODE

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

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

Note *2: These registers are accessible only when LCR bit-7 is set to a logic 1.

Rev. 3.20

10

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