AEG Electrolux ERN 2922 User Manual download pdf (Page 60)

NEI COMMUNICATIONS

111111

CAT Control

Yaesu

FRG

-8800 with

Commodore

C -64

Computer

By Kjell W.

Strom, SM6CPI

The microcomputer

brought

many ad-

vantages

to modern electronics. Commu-

nications is one area in

which

its benefits

can shine, especially if you have a corn -

munications receiver already equipped to

"communicate"

with

a computer. Such

a receiver is the popular Yaesu

FRG

-8800.

I'll show

you

how the Yaesu FRG -8800

general- coverage receiver can be con-

trolled

with

a Commodore C -64

(or

C -128 operated

the C -64

mode)

com-

puter. The problems associated

with

run-

ning the C -64 reliably at

the

undocu-

mented 4,800 -baud rate have been solved

using a machine -language routine,

which

is loaded from a BASIC program.

very

simple hardware solution for interfacing

between the computer and

the

shortwave

receiver is included here as

well.

The RS

-232

Mystery

Yaesu's CAT (Computer

Assisted Trans-

ceiver)

accepts commands sent to it in a

standard RS -232C format. This format

does not cause any

problems. Any ad-

vanced

book on the C -64

will

tell

you

how to set up the Command and Control

registers for a

word

length of eight bytes

with

two stop bits and

parity.

Though

the CAT system operates at

4,800

baud, the

computer's baud rate

stops at 2,400 baud.

Some available

liter-

ature gives formulas for

calculating

non-

standard baud rates. If you try plugging

in numbers,

you

will

arrive at the conclu-

sion that the maximum transfer rate is

bit

over 5,000 baud.

In point

fact,

you

can set up the C -64 for

4,800

baud

with

the parameters

calculated

from

these

for-

mulas. However, the result is not relia-

ble; sometimes characters get

lost

their

way

to the User Port.

In the

program

listed here, such prob-

lems are avoided by using the aforemen-

tioned machine -language routine for

handling the RS -232C procedures. There

is also a routine for converting the fre-

quency bytes from hexadecimal to deci-

mal format.

This

is necessary

because the

frequency bytes calculated

the pro-

+5V

330

ir)

7404

NOTE:

Connect

pins 3, 5, 9, and

on the

7404.

Fig. 1.

Schematic diagram of

interface

between

a Commodore C -64 computer and

Yaesu

FRG -8800 general- coverage shortwave

receiver.

gram are in hex format, while

the BASIC

interpreter

treats all numbers

as decimal

numbers.

You then get an

extra

decimal -

to -hex

conversion,

which

you must undo

by reconverting.

Reconversion

easily accomplished in

BASIC,

but the machine -language rou-

tine occupies less memory

space and is

several times faster than the BASIC

pro-

gram.

This

can be

important

in, for

ex-

ample, scanning procedures.

The machine

-language

part

of the

pro-

gram is loaded from

the DATA in lines

4110

through

4114

by the command

GOSUB 4000. There

are four SYS -call

entrances

to the

routines:

I.)

SYS 52480 is the 4,800 -baud

im-

proved version

of OPEN 1,2, . . .

2.) SYS

52512 takes the five bytes that

have been POKEd into temporary

stor-

age at locations

52592 through 52596,

does the hex -to- decimal

conversion on

52592 through

52596 and sends all five

bytes, like PRINT I.

3.) SYS 52526 sends

52592

through

52596

without

conversion, since you do

not

want

to reconvert

the

2 -byte

com-

mands.

4.)

SYS 52578

is functionally

equiva-

lent to CLOSE 1.

Main Program

Key in and

SAVE the program

listed

else-

where

in this column. Then type RUN

10000, followed

by a RETURN

to check

that the machine

-language routine's

DATA

have been

entered in good order.

Otherwise, you may lose

the program if

you try

RUN

without

first

saving

it.

(Note: If you

are having difficulty in in-

terpreting the reverse

block characters in

the

program, they are

follows:

Line

200

contains an R after

the first quota-

tion mark and QQ in quotes

at the end of

the line; Line 1050

also contains

an R

after the first

quotation mark

and

QQQQQQQ in quotes

at its

end; and

Line

1 115 contains

SQQQQQQ in quotes

after the first quotation

mark and has a

wide

cross graphics

character

quotes

just

before the final "A"

on the

line.)

The program

executes as follows:

Lines 100 through

500

initialize

the

program, open

the

-232C file and

set

up the first

selection screen.

Lines

1120 through 1295

detect com-

mands from the keyboard

and

perform

them

via

subroutines.

Lines 1300 through 1320

check that the

entered frequency is

in the proper format

and is

within

the range

of the

radio.

Lines 1700

through 1990 first

deter-

mine the

position of the decimal point

and then

slice up the frequency into four

two -digit

bytes,

POKE

them

into

tempo-

rary storage and send

them to the micro-

processor inside

the FRG -8800.

Lines 2000

through 2030

contain the

subroutine for

exiting the program.

/ MODERN ELECTRONICS / February 1988

Say You Saw It In Modern

Electronics

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