Rabbit 2000 - 2. Rabbit Design Features

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Designer’s

Handbook 9

4.

Dynamic

C

Rabbit

Programming

Overview

When

Dynamic

C

compiles

the

user’s

program

it

includes

a

BIOS

or

basic

input-output

system.

The

BIOS

a

fairly

small

piece

of

code

that

provides

a

variety

of

low

level

services

for

the

user’s

program.

The

BIOS

also

takes

care

of

microprocessor

system

initialization.

The

BIOS

provides

the

communications

services

required

by

Dynamic

C

for

downloading

code

and

performing

debugging

services

such

as

setting

breakpoints

or

examining

data

variables.The

BIOS

defines

the

setup

of

memory.

An

existing

BIOS

can

be

used

as

a

skel-

eton

BIOS

to

create

a

new

BIOS.

Frequently

it

will

only

be

necessary

to

change

#define

statements

at

the

beginning

of

the

BIOS.

In

this

case

it

is

unnecessary

for

the

user

to

understand

or

work

out

the

details

of

the

memory

setup

and

other

processor

initialization.

The

designer

should

follow

Rabbit

system

design

conventions

so

that

Dynamic

C

can

work

with

his

system.

The

design

conventions

are

listed

below.

• Include

a

standard

Rabbit

programming

cable

(see

Figure 1).

The

standard

10-pin

pro-

gramming

connector

provides

a

connection

to

serial

port

A

and

allows

the

PC

to

reset

and

cold-boot

the

target

system.

• Connect

a

static

RAM

having

at

least

32K

to

chip

select

#1

(/CS1,

/OE1,

/WE1).

It

is

useful

if

the

PC

board

footprint

can

also

accommodate

a

RAM

large

enough

to

hold

all

the

code

anticipated.

If

a

large

RAM

can

be

accommodated,

software

development

will

go

faster.

Although

code

residing

in

some

flash

memory

can

be

debugged,

debugging

and

program

download

is

faster

to

RAM.

There

are

also

types

of

flash

memory

that

can

be

used,

but

they

cannot

support

debugging.

• Connect

a

flash

memory

that

is

on

the

approved

list

and

has

at

least

128K

of

storage

to

chip

select

#0

(/CS0,

/OE0,

/WE0).

Nonapproved

memories

can

be

used,

but

it

may

be

necessary

to

modify

the

BIOS.

Some

systems

designed

to

have

their

program

reloaded

by

an

external

agent

on

each

powerup

may

not

need

any

flash

memory.

• Install

a

crystal

or

oscillator

with

a

frequency

of

32.768

kHz

to

drive

the

battery-back-

able

clock.

(Battery-backing

is

optional,

but

the

clock

is

used

in

the

cold-boot

sequence

to

generate

a

known

baud

rate.)

• Install

a

crystal

or

oscillator

for

the

main

processor

clock

that

is

a

multiple

of

614.4 kHz,

or

better,

a

multiple

of

1.8432

MHz.

These

preferred

clock

frequencies

make

possible

the

generation

of

sensible

baud

rates.

If

the

crystal

frequency

is

a

multi-

ple

of

614.4

kHz,

then

the

same

multiples

of

the

19,200

bps

baud

rate

are

achievable.

Common

crystal

frequencies

to

use

are

3.6864,

7.3728,

11.0592

or

14.7456

MHz,

or

double

these

frequencies.

The

user

may

be

concerned

that

the

requirement

for

a

programming

connector

places

added

cost

overhead

on

his

design.

The

overhead

is

very

small—less

than

$0.25

for

com-

ponents

and

board

space

that

could

be

eliminated

if

the

programming

connector

were

not

made

a

part

of

the

system.

• The

programming

connector

can

also

be

used

for

a

variety

of

other

purposes,

including

user

applications.

A

device

attached

to

the

programming

connector

has

complete

con-

trol

over

the

system

because

it

can

perform

a

hardware

reset

and

load

new

software.

If

Table of Contents

Other manuals for Rabbit 2000

User Manual230 pages

Instruction & Reference Manual174 pages

Reference Manual120 pages

Getting Started Manual54 pages

Getting Started43 pages