XR16C854 Datasheet, PDF(5/51 Page) Exar Corporation – QUAD UART WITH RX/TX FIFO COUNTERS,128-BYTE FIFO

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XR16C854 Datasheet, PDF (5/51 Pages) Exar Corporation – QUAD UART WITH RX/TX FIFO COUNTERS,128-BYTE FIFO

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XR16C854

SYMBOL DESCRIPTION

Symbol

16/-68

A3-A4

CLKSEL

-CS

Signal

68 100 64 type

Pin Description

31 36

I 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 16C554

is selected. When this pin is a logic 0, the 68 mode interface

(68C554) 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-ORÂ

configuration. The WIRE-OR outputs are connected inter-

nally to the open source IRQ signal output. This pin is not

available on 64 pin packages which operate in the 16 mode

only.

34 39 24

I Address-0 Select Bit. Internal registers address selection in

16 and 68 modes.

33 38 23

I Address-1 Select Bit. Internal registers address selection in

16 and 68 modes.

32 37 22

I Address-2 Select Bit. - Internal registers address selection

in 16 and 68 modes.

20,50 17,64 -

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

these pins are used to address or select individual UARTÂs

(providing -CS is a logic 0). In the 16 mode, these pins are

reassigned as chip selects, see -CSB and -CSC. These pins

are not available on 64 pin packages which operate in the

16 mode only.

30 35

I Clock Select. - The 1X or 4X pre-scaleable clock is selected

by this pin. The 1X clock is selected when CLKSEL is a logic

1 (connected to VCC) or the 4X is selected when CLKSEL

is a logic 0 (connected to GND). MCR bit-7 can override the

state of this pin following reset or initialization (see MCR bit-

7). This pin is not available on 64 pin packages which

provide MCR bit-7 selection only.

16 13

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

as a multiple channel chip enable. In this case, all four

Rev. 1.00P

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