XR16V2650_07 Datasheet, PDF (7/47 Pages) Exar Corporation – HIGH PERFORMANCE DUART WITH 32-BYTE FIFO

XR16V2650
REV. 1.0.2
HIGH PERFORMANCE DUART WITH 32-BYTE FIFO
2.0 FUNCTIONAL DESCRIPTIONS
2.1 CPU Interface
The CPU interface is 8 data bits wide with 3 address lines and control signals to execute data bus read and
write transactions. The V2650 data interface supports the Intel compatible types of CPUs and it is compatible
to the industry standard 16C550 UART. No clock (oscillator nor external clock) is required to operate a data
bus transaction. Each bus cycle is asynchronous using CS#, IOR# and IOW# signals. Both UART channels
share the same data bus for host operations. The data bus interconnections are shown in Figure 3.
FIGURE 3. XR16V2650 DATA BUS INTERCONNECTIONS
D0
D1
D2
D3
D4
D5
D6
D7
A0
A1
A2
IO R #
IO W #
UART_CSA#
UART_CSB#
UART_INTA
UART_INTB
TXRDYA#
RXRDYA#
TXRDYB#
RXRDYB#
UART_RESET
D0
D1
D2
D3
D4
D5
D6
D7
A0
A1
A2
IO R #
IO W #
CSA#
CSB#
INTA
INTB
TXRDYA#
RXRDYA#
TXRDYB#
RXRDYB#
VCC
UART
Channel A
TXA
RXA
DTRA#
RTSA#
CTSA#
DSRA#
CDA#
RIA#
OP2A#
UART
Channel B
TXB
RXB
DTRB#
RTSB#
CTSB#
DSRB#
CDB#
RIB#
OP2B#
RESET
GND
VCC
Serial Interface of
RS-232, RS-422
Serial Interface of
RS-232, RS-422
2.2 5-Volt Tolerant Inputs
The V2650 can accept up to 5V inputs even when operating at 3.3V or 2.5V. But note that if the V2650 is
operating at 2.5V, its V_OH may not be high enough to meet the requirements of the V_IH of a CPU or a serial
transceiver that is operating at 5V.
2.3 Device Reset
The RESET input resets the internal registers and the serial interface outputs in both channels to their default
state (see Table 15). An active high pulse of longer than 40 ns duration will be required to activate the reset
function in the device.
2.4 Device Identification and Revision
The XR16V2650 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 (DLD = 0xXX). Now reading the content of the DVID will
provide 0x06 for the XR16V2650 and reading the content of DREV will provide the revision of the part; for
example, a reading of 0x01 means revision A.
2.5 Channel A and B Selection
The UART provides the user with the capability to bi-directionally transfer information between an external
CPU and an external serial communication device. A LOW signal on the chip select pins, CSA# or CSB#,
allows the user to select UART channel A or B to configure, send transmit data and/or unload receive data to/
from the UART. Selecting both UARTs can be useful during power up initialization to write to the same internal
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