NS486SXL Datasheet, PDF (6/26 Pages) National Semiconductor (TI) – Optimized 32-Bit 486-Class Controller with On-Chip Peripherals for Embedded Systems

1.0 System Overview (Continued)
Finally, the Bus Interface Unit also provides signals to indi-
cate bus activity and control (optional) data bus transceiver
direction. The bus direction signal, and chip selects continue
to operate correctly during external master accesses.
1.5 OTHER ON-BOARD PERIPHERALS
In addition to those peripherals and system control elements
needed for System Service Elements, the NS486SXL also
includes a number of I/O controllers and resources that
make implementing a complete embedded system possible
with just a single-chip NS486SXL controller. These include a
serial UART port, and a MICROWIRE or Access.bus syn-
chronous serial bus interface.
1.5.1 Reconfigurable I/O Lines
The NS486SXL supports reconfigurable I/O. For example, if
the UART, interrupts, or other functions are not being used,
the I/O pins associated with them can be reconfigured as
general purpose bidirectional I/O pins. Up to 28 pins can be
reconfigured for this purpose. This capability makes the
NS486SXL extremely versatile and ideal for supporting dif-
ferent end product configurations with a single NS486SXL
device.
1.5.2 MICROWIRE/Access.bus Interface
The NS486SXL MICROWIRE/Access.bus interface provides
for full support of either the three-wire MICROWIRE or the
two-wire Access.bus serial interfaces. MICROWIRE has an
alternate clock phasing option that supports the SPI bus pro-
tocol as well. These industry standard interfaces permit easy
interfacing to a wide range of low-cost specialty memories
and I/O devices. These include EEPROMs, SRAMs, timers,
clock chips, A/D converters, D/A converters, and peripheral
device drivers.
1.5.3 UART Serial Port
The NS486SXL UART provides complete NS16550 (PC
standard) serial communications port compatibility including
the performance enhancing 16-byte deep FIFO. It performs
serial-to-parallel conversion from external devices to the
NS486SXL and parallel-to-serial conversion from the
NS486SXL to external peripherals. Full modem control can
be supported.
A serial IrDA v1.0 and HP-SIR (infrared) mode is also sup-
ported, making possible low-cost wireless communications
between an NS486SXL-based system and other wireless in-
frared systems.
1.6 ICE SUPPORT
National Semiconductor has worked closely with Microtek In-
ternational to provide hardware in-circuit emulator support
for the NS486SXL. The Microtek product (PowerPack^® EA-
NS486) uses a special bondout version of the NS486SXL to
deliver a full-featured hardware emulator that is capable of
tracing on chip activity, including peripheral interrupt and I/O
activity. The emulator runs at full speed, and supports over-
lay memory and multiple triggers.
1.7 OTHER ISSUES
NS486SXL provides a comprehensive set of on-board pe-
ripherals. Also, it is designed to easily interface to external
peripherals. In addition to this ISA-like bus which supports
ISA-compatible peripherals, the NS486SXL provides an in-
terface to an external master with a shared memory space.
The external master or auxiliary processor interface allows
low cost interfacing to shared external memory belonging to
other external masters (including another NS486SXL con-
troller).
To program the resources of the NS486SXL, a set of internal
control registers exists. These registers provide precise con-
trol over all internal resources and the setup of external
NS486SXL control signals. It is the designer’s responsibility
to ensure the proper initialization of the registers in this I/O
map.
In addition, the NS486SXL core processor itself requires
several descriptor tables and initialization parameters that
must be set by user-written start-up software.
The NS486SXL is designed from the ground up for optimum
price/performance in embedded systems. This makes the
NS486SXL the logical choice as the base hardware platform
for executing an embedded operating system kernel such as
those available from Microtec International, Wind River, ISI,
QNX, and many others. Any Operating System or Real-Time
Executive that will operate in a segmented or flat memory
model protect mode environment is a suitable complement
to the NS486SXL.
Also, there are many third party tool sets that will allow an
executable application to be built to run directly on the target
hardware without an O/S environment.
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