/prog/ - MIX ENTA

Name: smakka 2007-04-25 12:36 ID:qT55Uyd9

Hello - Can anyone help me understand the ENTA instruction from the MIX computer. I dont understand the part about when M=0.

FYI, the description of it is:

"ENTA (Enter A) C = 48; F = 2.
The quantity M is loaded into rA. The action is equivalent to "LDA" from a memory word containing the signed value of M. If M=0, the sign of the instruction is loaded."

what instruction is loaded?

Name: Anonymous 2007-04-25 12:56 ID:L9DjIXj2

It just loads the value of M (rather than the value at location M) into register A.

Name: smakka 2007-04-25 13:12 ID:qT55Uyd9

Yes, but what about the bit when M=0?

Name: Anonymous 2007-04-25 13:18 ID:Heaven

>>3
M / 0

Name: Anonymous 2007-04-25 13:49 ID:EBDetUIQ

"sign of the instruction"?

instructions have signs?

Name: smakka 2007-04-25 14:44 ID:qT55Uyd9

Yes, these ones do.

My best guess now is that its talking about the sign of the zero - ie. whether it is positive or negative zero

Name: Anonymous 2007-04-25 14:50 ID:BUzv0QAS

>>3

I think it's just pointing out that the sign is always copied, even when M = 0.

Name: Anonymous 2007-04-25 14:52 ID:BUzv0QAS

>>5

See http://www.gnu.org/software/mdk/manual/mdk.html

Name: smakka 2007-04-25 15:35 ID:qT55Uyd9

thanks.. that's what i thought too.

Name: Anonymous 2007-04-25 17:01 ID:Xgyl5h3v

NO EXCEPTIONS

Name: Anonymous 2007-04-25 17:36 ID:iWjLPSVO

>>7
When M = 0, the sign is the ONLY thing copied. That way you can negate a number just by using the instruction to replace the sign bit.

Name: Anonymous 2007-04-25 17:54 ID:BUzv0QAS

>>11

What instruction would you use for storing +0 into register A then?

Name: Anonymous 2007-04-25 20:02 ID:cKRO0x/K

>>12

I've never actually looked at this, but I'm guessing it probably involves xor.

Name: Anonymous 2007-04-26 5:04 ID:bRfDjWQq

>>13

Does MIX have an xor instruction?

Name: smakka 2007-04-26 14:34 ID:rFQIsF9N

no it does not

MIX ENTA

1 Name: smakka 2007-04-25 12:36 ID:qT55Uyd9

2 Name: Anonymous 2007-04-25 12:56 ID:L9DjIXj2

3 Name: smakka 2007-04-25 13:12 ID:qT55Uyd9

4 Name: Anonymous 2007-04-25 13:18 ID:Heaven

5 Name: Anonymous 2007-04-25 13:49 ID:EBDetUIQ

6 Name: smakka 2007-04-25 14:44 ID:qT55Uyd9

7 Name: Anonymous 2007-04-25 14:50 ID:BUzv0QAS

8 Name: Anonymous 2007-04-25 14:52 ID:BUzv0QAS

9 Name: smakka 2007-04-25 15:35 ID:qT55Uyd9

10 Name: Anonymous 2007-04-25 17:01 ID:Xgyl5h3v

11 Name: Anonymous 2007-04-25 17:36 ID:iWjLPSVO

12 Name: Anonymous 2007-04-25 17:54 ID:BUzv0QAS

13 Name: Anonymous 2007-04-25 20:02 ID:cKRO0x/K

14 Name: Anonymous 2007-04-26 5:04 ID:bRfDjWQq

15 Name: smakka 2007-04-26 14:34 ID:rFQIsF9N