XR16L651 Datasheet, PDF (3/56 Pages) Exar Corporation – 2.25V TO 5.5V UART WITH 32-BYTE FIFO

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PIN DESCRIPTIONS
XR16L651
2.25V TO 5.5V UART WITH 32-BYTE FIFO
NAME
PIN #
TYPE
DESCRIPTION
16 (Intel) or 68 (Motorola) MODE DATA BUS INTERFACE. The PCMODE# pin is connected to VCC.
A2
26
I Address bus lines [2:0]
A1
27
A2:A0 selects internal UART’s configuration registers.
A0
28
D7
4
IO Data bus lines [7:0] (bidirectional)
D6
3
D5
2
D4
48
D3
47
D2
46
D1
45
D0
44
IOR#
19
I Input/Output Read (active low)
When IM# pin is at logic 0, it selects Intel bus interface and this input is read
strobe (active low). The falling edge instigates an internal read cycle and
retrieves the data byte from an internal register pointed by the address lines
[A2:A0], places it on the data bus to allow the host processor to read it on the
leading edge. When IM# pin is at logic 1, it selects Motorola bus interface and
the IOR# input is not used and it should be connected to GND to minimize
supply current. Its function is the same as IOR, except it is active low. Either
an active IOR# or IOR is required to transfer data from 651 to CPU during a
read operation. If this input is unused in the Intel bus mode (IM# pin is at
logic 0), it should be connected to VCC to minimize supply current.
IOR
20
I Input/Output Read (active high)
Same as IOR# but active high. When IM# pin is at logic 1 for Motorola bus
mode, this pin is not used and should be connected to GND to minimize sup-
ply current. If this input is unused in the Intel bus mode (IM# pin is at logic 0),
it should be connected to GND to minimize supply current.
IOW#
(R/W#)
16
I Input/Output Write (active low) - Intel bus mode
When IM# pin is at logic 0, it selects the Intel bus interface and this input
becomes the write strobe (active low). The falling edge instigates the internal
write cycle and the trailing edge transfers the data byte on the data bus to an
internal register pointed by the address lines [A2:A0]. Its function is the same
as IOW, except it is active low. Either an active IOW# or IOW is required to
transfer data from 651 to the Intel type CPU during a write operation. If this
input is unused (in the Intel bus mode), it should be connected to VCC to min-
imize supply current.
Read/Write Strobe - Motorola bus mode
When IM# pin is at logic 1, it selects Motorola bus interface and this input
becomes R/W# signal for read (logic 1) and write (logic 0).
IOW
17
I Input/Output Write (active high)
Same as IOW# but active high. When IM# pin is at logic 1 for Motorola bus
mode, this pin must be connected to GND to allow IOW# input to function cor-
rectly. If this input is unused in the Intel bus mode (IM# pin is at logic 0), it
should be connected to GND to minimize supply current.
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