XR16L651
á
2.25V TO 5.5V UART WITH 32-BYTE FIFO
REV. 1.3.0
4
CS0
9
I
Chip Select 0 input (active high)
This input selects the XR16L651 device. If CS1 or CS2# is used as the chip
select then this pin must be connected to VCC. The 651 is selected when all
three chip selects are active. See
CS1
10
I
Chip Select 1 input (active high)
This input selects the XR16L651 device. If CS0 or CS2# is used as the chip
select then this pin must be connected to VCC. The 651 is selected when all
three chip selects are active. See
CS2#
11
I
Chip Select 2 input (active low)
This input selects the XR16L651 device. If CS0 or CS1 is used as the chip
select then this pin must be connected to GND. The 651 is selected when all
three chip selects are active. See
INT
(INT#)
30
O
Interrupt Output
This output becomes active whenever the transmitter, receiver, line and/or
modem status register has an active condition. See interrupt section for more
details. When IM# pin is at logic 0 (Intel bus mode), this interrupt output may
be set to normal active high or active high open source to provide wire-OR
capability by connecting a 1k to 10k ohms resistor between this pin and
ground. When IM# pin is at logic 1 (Motorola bus mode), this interrupt output
becomes an open drain, active low output. It requires an external pull-up
resistor of 1K-10K ohms to operate properly. The output may be wire-OR’ed
with other devices in the system to form a single interrupt request to the host
processor and have the software driver poll all devices to determine the inter-
rupting condition(s).
AS#
24
I
Address Strobe input (active low)
In the Intel bus mode, the leading-edge transition of AS# latches the chip
selects (CS0, CS1, CS2#) and the address lines A0, A1 and A2. This input is
used when the address lines are not stable for the duration of a read or write
operation. In devices with top mark date code of "C2 YYWW" and newer, the
address bus is latched even if this input is not used. These devices feature a
If not required, this input can be permanently tied to GND. This input is not
used in the Motorola mode.
TXRDY#
23
O
UART Transmitter Ready (active low)
The output provides the TX FIFO/THR status. See
leave it unconnected.
RXRDY#
29
O
UART Receiver Ready (active low)
This output provides the RX FIFO/RHR status for receive channel A. See
Table 2. If it is not used, leave it unconnected.
PC Mode Interface Signals. Connect PCMODE# pin to GND and IM# pin to GND to select PC Mode.
A3
A4
A5
A6
A7
A8
A9
20
6
9
10
11
17
38
I
PC mode additional Address Lines
In the PC mode, these are the additional address lines from the host address
bus. They are inputs to the on-board chip select decode function for COM 1-4
and LPT ports. See
Table 1 for details. The pins A4 and A9 have internal
100k
pull-up resistors.
NAME
PIN #TYPE
DESCRIPTION