NS486SXF datasheet(8/44 Pages) NSC

8 / 44 page

10 System Overview (Continued)

When the CPU is in idle mode the BIU is designed to mimic

the CPU during DMA interchanges between memory and

peripherals By responding to DRQs and generating DACK

and HOLDA signals as required the BIU eliminates the

need to reactivate the CPU during such transfers as screen

updates from memory to the LCD controller This gives the

designer added flexibility in conserving power while main-

taining basic system functions

15 OTHER ON-BOARD PERIPHERALS

In addition to those peripherals and system control ele-

ments needed for System Service Elements the NS486SXF

also includes a number of IO controllers and resources

that make implementing a complete embedded system pos-

sible with just a single-chip NS486SXF controller These in-

clude an IEEE 1284 Extended Capabilities Port a serial

UART port a LCD controller a PCMCIA interface and a

MICROWIRE or Accessbus synchronous serial bus inter-

face In addition unused IO controllers free up their IO

pins for general purpose use

151 Reconfigurable IO Lines

The NS486SXF supports reconfigurable IO For example if

the UART ECP Parallel Port LCD or PCMCIA functions are

not being used the IO pins associated with them can be

reconfigured as general purpose bidirectional IO pins Up

to 29 pins can be reconfigured for this purpose This capa-

bility makes the NS486SXF extremely versatile and ideal for

supporting different end product configurations with a single

NS486SXF

device

152 IEEE 1284 Bidirectional Port

The NS486SXF parallel port is a multifunction 8-bit parallel

port that is compatible with the IEEE 1284 bidirectional par-

allel port standard The operation of the parallel port is set

by the content of the NS486SXF parallel port IO control

registers The port can operate in one of two modes a stan-

dard parallel port mode (PC compatible) or a full Extended

Capabilities Port (ECP) mode The NS486SXF ECP port can

support both Host and Slave ECP mode In slave mode the

NS486SXF

becomes a versatile microprocessor for parallel

IO peripheral devices

153 PCMCIA Interface

The NS486SXF PCMCIA interface supports the direct con-

nection of a single PCMCIA 20 IC card Exchange Card

Architecture (ExCA release 150) compatibility and eXecute

In Place (XIP) capability is also provided

Accessing the PCMCIA interface switches the external bus

automatically into the PCMCIA mode and permits Memory

Window Mapping and Address Offset to be handled inside

the NS486SXF device Power management and ‘‘hot’’ card

insertionremoval options can be implemented using exter-

nal buffering if required

154 MICROWIREAccessbus Interface

The NS486SXF MICROWIREAccessbus interface pro-

vides for full support of either the three-wire MICROWIRE or

the two-wire Accessbus serial interfaces MICROWIRE has

an alternate clock phasing option that supports the SPI bus

protocol as well These industry standard interfaces permit

easy interfacing to a wide range of low-cost specialty mem-

ories and IO devices These include EEPROMs SRAMs

timers clock chips AD converters DA converters and

peripheral device drivers

155 UART Serial Port

The NS486SXF 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

NS486SXF

and parallel-to-serial conversion from the

NS486SXF

to external peripherals Full modem control can

be supported

A serial IrDA v10 and HP-SIR (infrared) mode is also sup-

ported making possible low-cost wireless communications

between an NS486SXF-based system and other wireless

infrared systems

156 LCD Controller

The NS486SXF LCD controller is capable of controlling a

variety of monochrome supertwist LCD configurations in-

cluding 320x240 320x200 and 480x320 black and white or

grayscale graphics LCD modules equipped with self-con-

tained screen drivers It uses a video frame buffer in system

DRAM with either a 1- or 2-bit per pixel grayscale A 60 Hz

to 90 Hz frame refresh rate is supported Special controls

permit the fine tuning of display characteristics to precisely

optimize visual display quality

16 ICE SUPPORT

National Semiconductor has worked closely with Microtek

International to provide hardware in-circuit emulator support

for the NS486SXF The Microtek product (PowerPack

EA-

NS486) uses a special bondout version of the NS486SXF to

deliver a full-featured hardware emulator that is capable of

tracing on chip activity including peripheral interrupt and

IO activity The emulator runs at full speed and supports

overlay memory and multiple triggers

17 OTHER ISSUES

NS486SXF

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 NS486SXF 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 NS486SXF con-

troller)

To program the resources of the NS486SXF a set of inter-

nal control registers exists These registers provide precise

control over all internal resources and the setup of external

NS486SXF

control signals It is the designer’s responsibility

to ensure the proper initialization of the registers in this IO

map

In addition the NS486SXF core processor itself requires

several descriptor tables and initialization parameters that

must be set by user-written start-up software

The NS486SXF is designed from the ground up for optimum

priceperformance in embedded systems This makes the

NS486SXF

the logical choice as the base hardware plat-

form 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 com-

plement to the NS486SXF

Also there are many third party tool sets that will allow an

executable application to be built to run directly on the tar-

get hardware without an OS environment

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