January 12, 1998
1
Virtual IP Group, Inc.
1094 E. Duane Ave., Suite 211
Sunnyvale, CA 94086 USA
Phone:
+1 408-733-3344
Fax:
+1 408-733-9922
E-mail:
sales@virtualipgroup.com
URL: www.virtualipgroup.com
Features
Available under terms of the SignOnce IP License
Complete asynchronous communication protocol
includes:
-
5, 6, 7 or 8 bit data transmission
-
Even/odd or no parity bit generation and detection.
-
Start and stop bit generation and detection.
-
Line break detection and generation.
-
Receiver overrun and framing errors detection
Communications rates of up to 56K baud
Internal programmable baud rate generator
Buffered transmit and receive registers
Exception handling using interrupt/polled modes
Two Modes of operation - NS16450 and FIFO mode
Transmitter is buffered with 16 Byte FIFO
Receiver is buffered with 16 Byte FIFO plus 3 error bits
per data byte
Internal diagnostic capabilities with loopback
Modem handshake capability using CTS, RTS, DSR,
DTR, RI and DCD signals
Complete status reporting Capabilities
Line break generation and detection
Applications
Serial Communication Port
Modem Interface Port
AllianceCORE
TM
Facts
Core Specifics
Device Family
Spartan
XC4000E
CLBs Used
359
359
IOBs Used
38
1
38
1
System Clock fmax
16 MHz
16 MHz
Device Features
Used
Global Buffers
Supported Devices/Resources Remaining
I/O
CLBs
XCS40 PQ240-3
155
425
XC4020E HQ240-2
155
425
Provided with Core
Documentation
Core Design Document
FPGA Design Document
Design File Formats
NGD or XNF netlist
Verilog Source RTL
(available extra)
Constraint Files
.cst file, xactinit.dat.
Verification Tool
Test Vectors
Schematic Symbols
None
Evaluation Model
None
Reference designs &
application notes
FPGA Design Document
Additional Items
Evaluation Board available extra
Design Tool Requirements
Xilinx Core Tools
Alliance 1.3
Entry/Verification
Tool
Verilog RTL/Verilog XL simulator
Support
Support provided by Virtual IP Group, Inc.
Note:
1. Assuming all core signals are routed off-chip.
M16550A - Universal Asynchronous
Receiver/Transmitter With FIFOs
January 12, 1998
Product Specification
M16550A - Universal Asynchronous Receiver/Transmitter With FIFOs
2
January 12, 1998
General Description
The M16550A interfaces with a microcontroller or micro-
processor on one side and serial communications equip-
ment on the other. It provides full modem control through
easy handshaking with modems during communication.
Internal registers provide full programmability of serial
asynchronous communication parameters. It also imple-
ments exception detection and reporting to the processor
using interrupt or polled modes. The communication line
and modem status can be monitored at any time by the pro-
cessor by reading appropriate registers in the core.
Functional Description
This core emulates the functionality of National Semicon-
ductor's NS16550A. The block diagram with internal struc-
ture is shown in Figure 1.
System Interface and Control Block
This block supports the processor interface and generates
the internal system level signals for proper functioning.
LSR and LCR Block
This block holds the Line Status and Line Control Regis-
ters. These two registers control serial communication
capabilities of the core.
FCR Block
This block has the FIFO control register which controls the
parameters for the transmit and receive FIFOs.
Interrupt Control Block
This block handles all interrupt capabilities for the core.
Transmit and FIFO Block
This block holds the transmitter section and a 16-byte
transmit FIFO.
Baud Rate Generator Block
This block generates the Baud Rate Clock for the transmit-
ter section of the core. This clock can also be used by the
receiver block by connecting BAUDOUT to RCLKReceiver
and FIFO Block
This block handles reception for the core. The clock for this
block is provided by RCLK. This clock should be 16X the
Figure 1: M16550A Block Diagram
January 12, 1998
3
Virtual IP Group Inc.
Baud Rate. The receive data FIFO is included in this block
which stores 16 bytes at a time. The 16 bit FIFO's for status
parameters (parity, framing and break) for the correspond-
ing bytes in the receiver data FIFO is also included in this
block.
Modem Control Logic Block
This block handles the modem control capabilities for the
megacell core. These signals can be used for the commu-
nication purpose also some of the signals can be used as
general purpose signals (OUT1 and OUT2). The modem
control register resides in this block which provides the
internal diagnostic capability for the core.
Core Modifications
Modifications can be done to remove the internal baud rate
generator, or strip off either transmitter or receiver or size
the FIFO of Transmitter and Receiver separately. These
modifications can be performed by Virtual IP Group, Inc. for
additional cost.
Verification Methods
The core has been tested with in-house developed simula-
tion test vectors that are provided with the core. Assembly
level 80x86 programs were used to test the functionality of
the FPGA in hardware.
Recommended Design Experience
Knowledge of interface with Microprocessor based sys-
tems is required. The user must be familiar with HDL
design methodology as well as instantiation of Xilinx
netlists in a hierarchical design environment. Usage of Alli-
ance or Foundation tools is required.
Available Support Products
The FPGA Design Document included with the core gives
directions of constructing a general purpose FPGA evalua-
tion daughter board that can be plugged in to a standard
port socket on the target system through a flat cable.
Ordering Information
This AllianceCORE product is available from Xilinx Alli-
anceCORE partner, Virtual IP Group, Inc., under terms of
the SignOnce IP License. To learn about the SignOnce IP
License program, contact Virtual IP Group, visit www.xil-
inx.com/ipcenter/signonce.htm, or write to commonli-
cense@xilinx.com.
Please contact Virtual IP Group, Inc. for pricing and addi-
tional information about this AllianceCORE product.
Related Information
Refer to Specification Document for programming of this
core for a typical application in a system. The user is
required to refer to Designer's application note for integrat-
ing this core with other cores.
Xilinx Programmable Logic
For information on Xilinx programmable logic or develop-
ment system software, contact your local Xilinx sales office,
or:
Xilinx, Inc.
2100 Logic Drive
San Jose, CA 95124
Phone:
+1 408-559-7778
Fax:
+1 408-559-7114
URL:
www.xilinx.com
For general Xilinx literature, contact:
Phone:
+1 800-231-3386 (inside the US)
+1 408-879-5017 (outside the US)
E-mail:literature@xilinx.com
M16550A - Universal Asynchronous Receiver/Transmitter With FIFOs
4
January 12, 1998
Pinout
The pinout has not been fixed to specific FPGA I/O allowing
flexibility with the users application. The evaluation board
pinout, however has been fixed. This information is includ-
ed in the design documentation. Signal names are provided
in Figure 1 and described in Table 1.
Table 1: Core Signal Pinout
Signal
Signal Direction
Description
System Interface Signals
A0, A1, A2
Input
Address signals to select an internal register for read/write operations.
CS0-2
Input
Chip Select. CS0 and CS1 are active high, CS2 is active low.
ADS
Input
Address Strobe. Chip Select, and address signals are latched internally on
rising edge of
ADS
. Pulled low if unused.
MR
Input
Master Reset Signal, active high.
RD
Input
Control, active high. Pulled low if unused.
RD
Input
Control, active low. Pulled high if unused.
WR
Input
Control, active high. Pulled low if unused.
WR
Input
Write Control, active low. Pulled high if unused.
DDIS
Output
Driver DISable signal, driven low, when core outputs data. Used to control
data flow direction intransceiver, or tristate buffers enable control.
CSOUT
Output
Indicates read/write selection of UART, active high and remains high when
UART is selected through chip select inputs.
XIN
Input
Master clock input.
XOUT
Input
Master clock output, inverted from XIN.
D7 - D0
In/Out
Bidirectional databus carries data to be written to internal registers; also
reports status of registers during read cycle.
Modem Interface Signals
RTS
Output
Active low REQUEST TO SEND indicates UART is ready to exchange da-
ta. System controls this pin through bit in modem control register.
CTS
Input
Active low CLEAR TO SEND indicates modem is ready to exchange data.
Present state monitored by reading MSR.
DTR
Output
Active low DATA TERMINAL READY tells modem that UART is ready to
establish communication link. System controls this pin by programming a
bit in MSR.
DSR
Input
Active low DATA SET READY indicates modem is ready to handshake
with core. Present state monitored by reading MSR.
DCD
Input
Active low DATA CARRIER DETECT indicates modem has detected car-
rier on communications line. Present state monitored by reading MSR.
RI
Input
Active low RING INDICATOR indicates modem has detected ring signal.
Present state monitored by reading MSR.
OUT1-2
Output
General purpose outputs. System controls these pins by through bit in
MSR.
Transmit/Receive Signals
SOUT
Output
Serial data output from transmitter block.
RCLK
Input
Input receive clock, should be 16 times communications baud rate.
SIN
Input
Serial data input for receiver block.
Other Signals
INTR
Output
Active high interrupt signal.
BAUDOUT
Output
Baud rate generator output clock.16 times the programmed communica-
tion baud rate.
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