sx20ac Parallax, Inc., sx20ac Datasheet - Page 4

• Manufacturer Part Number: sx20ac
• Description: Configurable Communications Controllers With Ee/flash Program Memory, In-system Programming Capability And On-chip Debug
• Manufacturer: Parallax, Inc.

Parallax SX20AC/SX28AC
1.3.
The SX devices use a modified Harvard architecture. This
architecture uses two separate memories with separate
address buses, one for the program and one for data, while
allowing transfer of data from program memory to
SRAM. This ability allows accessing data tables from
program memory. The advantage of this architecture is
that instruction fetch and memory transfers can be
overlapped with a multi-stage pipeline, which means the
next instruction can be fetched from program memory
while the current instruction is being executed using data
from the data memory.
This RISC-like architecture and memory design is based
on technology that makes it very fast, deterministic, jitter
free, and totally reprogrammable.
The SX family implements a four-stage pipeline (fetch,
decode, execute, and write back), which results in
execution of one instruction per clock cycle. For example,
at the maximum operating frequency of 75 MHz,
instructions are executed at the rate of one per 13.3 ns
clock cycle.
1.4.
and High-Level Languages
The SX’s high speed enables a “software system on a
chip” approach. Programming in assembly language
provides a particularly high-level of access to the interrupt
service routine, the stack and registers to take the highest
advantage of the SX’s deterministic timing. The primary
technical resources for programming the SX in assembly
language include the following:
Customers with a high-level programming language
background may prefer the use of a C or BASIC
compiler.
1.4.1.
Parallax's SX/B is a free BASIC language compiler for
the SX microcontroller (SX20, SX28, and SX48). The
compiler
microcontrollers by providing a simple, yet robust high-
level language familiar to Parallax customers. SX/B
includes the following features and commands:
© Parallax Inc.
• The SX20AC/SX28AC datasheet
• SX-Key Development System User’s Manual by
• Programming the SX Microcontroller – A Complete
• ASM directive to support in-line assembly language
• Program structure commands including BRANCH,
• Numeric formatters
• WORD variable support
• Frequency generation with FREQOUT
Parallax, Inc.
Guide by Guenther Daubach
DO..LOOP, GOTO, GOSUB, IF..THEN..ELSE
Architecture
Programming Benefits in Assembly
Parallax SX/B Basic Compiler
speeds
the
programming
of
the
SX
Page 4 of 51
The complete SX/B command reference and examples are
installed with the SX-Key IDE.
1.5.
Support
The SX devices are supported by Parallax’s programming
and debugging tools. The Parallax SX-Blitz is a
programming tool. The SX-Key supports programming
and source-level debugging. On-chip in-system debug
capabilities allow the Parallax tool to be an all-in-one
integrated development environment with editor, macro
assembler, debugger, and programmer. Unobtrusive in-
system programming is provided through the OSC pins.
Visit www.parallax.com for the SX-Key development
tools, the IDE and support forum information.
The in-system programming specification is available to
other 3rd party tool vendors upon request.
1.6.
The SX may be used as a solution for process controllers,
electronic appliances/tools, security/monitoring systems,
sound and signal generation, GPS interface, robotic
control, motor control, sensor interfacing and personal
communication devices. Applications such as interactive
toys, magnetic-stripe readers, infrared decoders, and other
timing-sensitive projects are also common with the SX.
Examples of customer applications may be seen on the
Parallax web site.
1.7.
Parallax and our distributors provide all support for the
SX microcontroller. Support is available free of charge
via phone [phone] in the U.S. Also be sure to
participate
http://forums.parallax.com/forums/.
support community is actively involved in customer
support 24 hours a day.
• Synchronous serial communication for I
• Asynchronous serial communication with SERIN
• Table data storage and retrieval with LOOKUP,
•
• Timing and delay with PAUSE, SLEEP
• PULSIN and PULSOUT
• Resistor/capacitor A/D with RCTIME
• RANDOM for pseudo-random number generation
• Non-volatile EEPROM memory access with DATA,
• Low-current SLEEP command
SPI
and SEROUT
LOOKDOWN
REVERSE
READ
I/O pin control with HIGH, LOW, TOGGLE,
Programming and Debugging
Applications
Support
in
the
SX
discussion
Rev 1.6 11/20/2006
The
www.parallax.com
on-line
2
forum
C, 1-Wire,
SX
at