Why does this work?

[volvo_0ne]

Rem AMOS Pro 2,00

Rem WHY DOES THIS WORK? 
Rem AS DEEKS & DOKES are to odd addresses???  


Reserve As Data 5,1000

ST=Start(5)+1

N=1

For I=ST To ST+31 Step 2

	Doke I,N
   
	Print I;",";Deek(I)
 
	N=N*2

Next I

[jotd]

it works because amos can read byte per byte and rebuild the 16 bit word... My Oric already had DEEK & DOKE and was 8 bit.

[volvo_0ne]

Originally Posted by jotd

it works because amos can read byte per byte and rebuild the 16 bit word... My Oric already had DEEK & DOKE and was 8 bit.

Yes, BUT in the manual, it says .....

DEEK function: read two bytes from an even address

word=Deek(address)

DEEK reads a two-byte "word" at a specified address.
This address must be even, or an address error will be generated.


DOKE instruction: change a two-byte word at an even address

Doke address,number

Use the DOKE command to copy a two-byte number between 0 and 65535 into the memory location at a specified even address.

Only DOKE into places where you are certain of safety, because indiscriminate use of this command will almost certainly crash your Amiga!

(My Underlines)
It does not throw up an "address error" and it seems to work ok in this case.

[jotd]

oh then it works because you're using a 68020+. 68020 and higher are able to read words on odd addresses.

[volvo_0ne]

Originally Posted by jotd

oh then it works because you're using a 68020+. 68020 and higher are able to read words on odd addresses.

AH!

I didn't know that.

I am indeed using an A1200 environment and AMOS 2.00

But even so (leading on to my next question)...........

Sometimes this seems very flaky.

Is there a way of writing/reading a mixture of 8/16 bit integers to consecutive memory locations reliably (odd or even) on all 68X?


for instance I may have sequence $F0 $00 $E710 to be saved (& retrieved) from arbitory addresses as 8 or 16 bit numbers (obviously $E710 is 16 bit & the others are 8 bit)


How would I deal with this without wasting the odd addresses?

I'll never need a number above $FFFF but I could waste a LOT of space by aligning and losing the odd bytes

[jotd]

use custom DOKE (resp DEEK):

POKE(address,(value / 256) & 0xFF);
POKE(address+1,value & 0xFF);

(not sure how masking is done in AMOS)

[volvo_0ne]

Thanks, that has solved my problem nicely

for reference......
I did

Poke address,value and $FF
Poke address+1,(value / 256) and $FF

to enter the values

and

value =Peek(address)+256*Peek(address+1)

to retrieve the value.

[jotd]

With that, you'll get the same value when writing & reading but you're actually writing your data with the wrong endianness.

address must have MSB, so (value / 256), and address+1 must have LSB, so value and $FF.

Your 2 errors make up, but the data is written in the wrong endian direction.

Try a double POKE on an even address, then a real DEEK you'll see what I mean

[volvo_0ne]

Originally Posted by jotd

With that, you'll get the same value when writing & reading but you're actually writing your data with the wrong endianness.

address must have MSB, so (value / 256), and address+1 must have LSB, so value and $FF.

Your 2 errors make up, but the data is written in the wrong endian direction.

Try a double POKE on an even address, then a real DEEK you'll see what I mean

I realise that (now) but I was used to Z80 notation (from years back) which must have kicked in automatically

It works here just now and it's only for some location data which i'm trialing.

(Unless you can see any problems down the line).......