XR16C854CV EXAR [Exar Corporation], XR16C854CV Datasheet - Page 11

• Manufacturer Part Number: XR16C854CV
• Description: 2.97V TO 5.5V QUAD UART WITH 128-BYTE FIFO
• Manufacturer: EXAR [Exar Corporation]

xr
REV. 3.0.1
For devices that have top mark date code "F2 YYWW" and newer, the 854 can accept a voltage of up to 5.5V
on any of its inputs (except XTAL1) when operating from 2.97V to 5.5V. XTAL1 is not 5 volt tolerant. Devices
that have top mark date code "DC YYWW" and older do not have 5V tolerant inputs.
The RESET input resets the internal registers and the serial interface outputs in all four channels to their
default state (see
reset function in the device. Following a power-on reset or an external reset, the 854 is software compatible
with previous generation of UARTs, 16C454 and 16C554 and 16C654.
The XR16C854 provides a Device Identification code and a Device Revision code to distinguish the part from
other devices and revisions. To read the identification code from the part, it is required to set the baud rate
generator registers DLL and DLM both to 0x00. Now reading the content of the DLM will provide 0x14 for the
XR16C854 and reading the content of DLL will provide the revision of the part; for example, a reading of 0x01
means revision A.
The UART provides the user with the capability to bi-directionally transfer information between an external
CPU and an external serial communication device. During Intel Bus Mode (16/68# pin is connected to VCC), a
logic 0 on chip select pins, CSA#, CSB#, CSC# or CSD# allows the user to select UART channel A, B, C or D
to configure, send transmit data and/or unload receive data to/from the UART. Selecting all four UARTs can be
useful during power up initialization to write to the same internal registers, but do not attempt to read from all
four uarts simultaneously. Individual channel select functions are shown in
During Motorola Bus Mode (16/68# pin is connected to GND), the package interface pins are configured for
connection with Motorola, and other popular microprocessor bus types. In this mode the 854 decodes two
additional addresses, A3 and A4, to select one of the four UART ports. The A3 and A4 address decode
function is used only when in the Motorola Bus Mode.
2.2
2.3
2.4
2.5
5-Volt Tolerant Inputs
Device Reset
Device Identification and Revision
Channel Selection
Table
CSA#
1
0
1
1
1
0
18). An active high pulse of longer than 40 ns duration will be required to activate the
CS#
CSB#
1
0
0
0
0
1
1
0
1
1
0
T
T
ABLE
ABLE
N/A
A4
0
0
1
1
CSC#
1
1
1
0
1
0
1: C
2: C
N/A
A3
0
1
0
1
HANNEL
HANNEL
CSD#
1
1
1
1
0
0
A-D S
A-D S
11
See Table 2
Channel A selected
Channel B selected
Channel C selected
Channel D selected
UART de-selected
2.97V TO 5.5V QUAD UART WITH 128-BYTE FIFO
ELECT IN
ELECT IN
F
Channels A-D selected
UNCTION
Channel A selected
Channel B selected
Channel C selected
Channel D selected
UART de-selected
F
below.
16 M
68 M
UNCTION
ODE
ODE
Table 1
below.
XR16C854/854D