ST16C454(1994) Просмотр технического описания (PDF) - Exar Corporation

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ST16C454
(Rev.:1994)

QUAD UNIVERSAL ASYNCHRONOUS RECEIVER/TRANSMITTER (UART)

Exar Corporation 

ST16C454/68C454

SYMBOL DESCRIPTION

Symbol

16/-68

A0

A1

A2

A3-A4

-CS

-CS A-B

-CS C-D

Rev. 3.20

Pin

31

34

33

32

20,50

16

16,20

50,54

Signal

type

I

Pin Description

16/68 Interface Type Select (input with internal pull-up). - This

input provides the 16 (Intel) or 68 (Motorola) bus interface type

select. The functions of -IOR, -IOW, INT A-D, and -CS A-D are re-

assigned with the logical state of this pin. When this pin is a logic

1, the 16 mode interface ST16C454 is selected. When this pin is

a logic 0, the 68 mode interface (ST68C454) is selected. When this

pin is a logic 0, -IOW is re-assigned to R/-W, RESET is re-assigned

to -RESET, -IOR is not used, and INT A-D(s) are connected in a

WIRE-OR” configuration. The WIRE-OR outputs are connected

internally to the open source IRQ signal output.

I

Address-0 Select Bit. Internal registers address selection in 16 and

68 modes.

I

Address-1 Select Bit. Internal registers address selection in 16 and

68 modes.

I

Address-2 Select Bit. - Internal registers address selection in 16

and 68 modes.

I

Address 3-4 Select Bits. - When the 68 mode is selected, these

pins are used to address or select individual UART’s (providing -

CS is a logic 0). In the 16 mode, these pins are reassigned as chip

selects, see -CSB and -CSC.

I

Chip Select. (active low) - In the 68 mode, this pin functions as a

multiple channel chip enable. In this case, all four UART’s (A-D)

are enabled when the -CS pin is a logic 0. An individual UART

channel is selected by the data contents of address bits A3-A4.

When the 16 mode is selected, this pin functions as -CSA, see

definition under -CS A-B.

I

Chip Select A, B, C, D (active low) - This function is associated with

the 16 mode only, and for individual channels, “A” through “D.”

When in 16 Mode, these pins enable data transfers between the

user CPU and the ST16C454 for the channel(s) addressed.

Individual UART sections (A, B, C, D) are addressed by providing

a logic 0 on the respective -CS A-D pin. When the 68 mode is

selected, the functions of these pins are reassigned. 68 mode

functions are described under the their respective name/pin

headings.

4

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