ZX Ferrum #02 26 апреля 2004

Железо

Iron - locking scheme buggy ports on the Scorpion and Profi.

An excerpt from the magazine ZX-Element # 1


                      SpellBbinder present


                    REVOLUTION on Speccy!!!


  Forgive me readers for such a grandiose name, but the idea
this development somewhat uncommon.

  Now seriously. It's no secret that the additional
ports on computers other than the benefits (additional memory,
Disable ROM, etc.) bring to users and headache, and
namely the need to block them. Otherwise, do not go
Some bend and demos. The proposed schemes to combat this
is placed in a rigid decryption of data ports and are
a useful addition to the computer's circuitry, but do not solve
problem completely. When you access the ports on the short 
address still having problems.


For example: LD A, # DF

          OUT (# FD), A

port work of Professor (# DFFD). Even more unfortunate 
situation in SCORPIO:


STS 3.3 makes it so

          LD A, # 1F

          OUT (# FD), A

Of course, he also wants to include the 7-th bank, but 
ironically (or creators Scorpio) responds port # 1FFD and 
computer freezes well. About PENTAGON-512 I do not say.



  So comrades, now it's over! The proposed scheme
"Monitors" command and blocks a short address at the time
its performance, all critical ports. That allows not
use the buttons to block ports.


                 DD2

                          +5 V
D0
D1 '

           DD1 S _____
D2 1 o R Q BLOK

D4 o D _o
           DD1 C Q
D5 1 o

                           DD3
D6
D7 DD1-1533LN1
_ DD2-1533LA2
M1 DD3-1533TM2


  The scheme works is simple: teams short of addressing all
two: it's IN A, (NN) - # DB and OUT (NN), A - # D3. They 
otlichyayutsya just one bit - D3, it we just will not start. 
When a on the data bus byte # DB # D3, or the output will LN2

logic 0. If the byte code operations recovered
processor, the signal of M1, he engages in TM2 to sleduyushego
cycle extraction operation code. If the processor finds any
another team, then TM2 locks logical 1. This
signal (BLOK) used to lock critical ports. A
so as to control the stiffness of the decryption of other ports
(Eg # 7FFD and muz.soprotsessora) allowing to have a tough
decoding in a long address and simplified for short.


  This scheme is tested on a PC PROS and scorpions, and
showed excellent results.



                       Opinion Editor:


  Simply unique and useful development.