Iron - Bugfix TR-DOS.

   Bugfix TR-DOS

(C) MAD MAX
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   Perhaps many (or rather,
almost all) faces
this unpleasant phenomenon - when
reading some of the programs drive heads violently hammered
at the end of the drive by issuing at
This heart-rending sounds. Why is this happening? What is it?
Controller error or error in the
program? Many people think of different ways. But here's 
Constantine Uglekov from Moscow (a huge thanks to him!) has 
decided to pay attention to this problem more seriously. We 
give its computation on the eliminate this defect, taken from a 
description of the Spectrum emulator. 


   On entering the subroutine # 3E44
(TR-DOS) in the register B should contain a constant position 
(from # 08 to # 0B); it makes OR # 18 and put the result in 
register controller commands (values # 18 - # 1B correspond 
to the Search command without checking the address markers on 
the track). When call # # 3EB5 3E44 from register B

not defined, and it can
contain, for example, the number of sectors when calling # 3D13 
with C = 5 or C = 6. If the number of sectors

more # 20, then in command register
will be directed not command code
SEARCH, but something else.

   A simple check shows
that everything is just so
manner. Causing # 3D13 with BC =
# 4005 a few times in a row (DE
believe unchanged), we can
monitor movements of the heads
drive one step closer to the center
disc before positioning in the
began to read the block, and when
Calls to 6005 BC = # observed
one step in the opposite direction.
If we consider that # 40 OR # 18 =
# 58 - command code step forward, and
# 60 OR # 18 - command code step back, then no doubt be
can - it is a mistake TR-DOS!

   Immediately follows the question -
is it possible to ruin a disc if
specify the number of sectors # A0-# BF
(To get the team record
sector), or # F0-# FF (to get the team track record)?
The answer - no. Even if the controller sees the number and # 
B8 # F8 as a legitimate team, to write to the disk has started, 
the controller must first get the first byte of data for

team records this sector bytes
must be received no later than the passage of the 8-th byte to 
the GAP writable sector, and to record the track - during the 
passage of 3 bytes of the filing team. If the first byte of data

is not received within that time frame, the operation 
immediately fails LOST DATA (data loss; bit 2 Status Register), 
and exhibited a signal IRQ (as

laid for the completion of any
operations). Once this error can not cause damage to the disc, 
then the question is: is it worth

it generally pay attention to?
If you are interested in improving
rate of exchange with the disk, then
definitely! All modifications TRDOS based on version 5.03 with 
pristavochkami type "FAST", "TURBO" etc. completely besmyssleny,

if each call to
Function 5.6 routines # 3D13
will be lost during either the positioning of (well, if
one step) or to search for the sector.


   What can you offer in return?
Instead of calling out # 3E44 # 3EB2 call something like # 880
(If there are empty), and at
# 880 put a small program:

PUSH HL; in H track number

            , Which is still needed
PUSH AF; the same observation
CALL # 3E08; registers HL and DE

            ; Will be broken, and

            ; DE can not Save.
LD B, A; finally in B

            , Gets a value

            ; Constant positioning
            ; Ning
POP AF
POP HL
JP # 3E44; and no mistake!


   To perform this refinement, you will have to erase the 
contents of the ROM and flash it again. For those ROMs that do 
not empty space (Scorpion), the variant of this piece of 
writing on some unnecessary text message, type "INTERFACE ONE 
FITTED". I wonder how many Scorpions with this interface?


   To the above should be added that this revision was made on 
a real Spectrum and showed their best way, without giving any 
side effects. And therefore it is recommended

for consumption.
________________________________
0 @ HA MP J `bF
. W

BB B B B B B B Btorov make it serviceability
LIMITED analog.

   Cons: Low speed data exchange; inability to recruit
number and establish a connection, complete lack of protection 
from interference in the line of transmission of individual 
characters. 



   About the same time with Peter in Moscow began to be sold
modem "Allegro." This device
worth while interest on
20 cheaper than vicomm, handkerchief
held every two and a half
less space, plugged it
on the tire itself skillfully recruit
number and make the connection. Programmatic support is also
was more developed, the rate of
also higher than vicomm, only
completely absent from the terminal mode. Therefore call
could only be friends with a similar unit, as
with modems of other types of "Allegro" can not communicate. In 
recent years, from Moscow to hear News that the "Allegro"

otkryvayutya BBS'ki. And as usual Spectrum BBS'ok used with 
disk drives. Personally, I am weak can imagine

how to make a full
BBS'ku on the Spectrum, if only because the amount of 
information every day passing through the network is so large 
that it does not enough for any drive.



   Two of my friends, the commercials
in 1993 they brought themselves from Moscow
this unit, and quite happily share each other's programs. So, 
for the user "Allegro" undoubtedly more convenient than vicomm, 
on because of more advanced designs and initially normal 
programmatic support. 



   However, both these options have one huge and irresistible
MINUS - Custom! And, having
vicomm or Allegro, you anyway
not be able to connect with a huge amount BBS'ok (if
they do not install special hardware support for your 
non-standard modem), or with one another, having ibm or Amiga.

Therefore, in my opinion, the most
preferred is the third
option - a connection to the Spectrum standard hayes modem.


   Connect a standard or customary ibm'schikam amizhnikam
hayes, you get a sweet opportunity not only to exchange
information with friends, having
similar device, but
call for a huge number of
BBS'ok your city or even
overseas (if a lot of money).
You will not be up all night to break,
making our way through the crowd wanting for one or two 
stations that work with your non-standard device and you will 
be able to choose a couple of stations (out of hundreds!) for 
yourself and get access to the huge mass of information.

Among the huge number of conferences on various topics you
can always choose something
interesting for you, whether it is
beer, women, books, jokes,
Program, automatic number detectors, magic ... or
something else of the many hundreds of topics.
You can find like-minded opponents, make an interesting debate 
and learn something new for yourself. And maybe you become an 
avid Fidoshnikom who can not imagine a day without fresh 
bundles of letters and will be difficult represent - as you 
used to lived without all this vast and

iteresneyshego world of electronic
mail addresses, without those friends from whom you are, 
perhaps, distant at thousands of miles and never

seen ...



   Seller vicomm'a Sergey Usov
as an argument against
hayes'ov said something like: "what's the use in a standard, if 
at all these hundreds of BBS, you can only read mail, files, 
there are ibm'ovskie. 


   My answer: The first - about BBS'ki:
currently working and have a file
areas for ZX-Spectrum programs:
BBS MONTEZUMA

   (2:5030 / 362)
ZX-Rise BBS

   (2:5030 / 178.47)
Dark Dragon Station

   (2:5030 / 362.2)
ASN Station

   (2:5030 / 362.3)


   This is one of those to which I climb, but if seem a little,
the list can easily be increased.
So far we have to suffice.

   Second: I absolutely can easily send the person Spectrum
program at ibm. There, he dragged them to the TR-DOS and looked.
Without hayes'a we would not have
Timeout.

              ____


   Now specifically about the hayes.
Hayes modems come in two types -
internal and external. They practically did not differ in
opportunities, only for the price and
connection. In addition,
hayes'ah found interesting
tsifrochki and shaped as letters. such as these:
 2400/mnp5/v42b

2400 - is the speed - 2400 baud;
mnp5/v42b - it's error correction and data compression.
Various combinations of these values in the ground and affect 
the cost of modems. 


   Standard speed - 2400
4800, 9600, 14400 and above.
Connected to the Spectrum modems
speeds greater than 14,400 may
original, but hardly justified, the price of domestic 2400/mnp5
/ V42b modem is about $ 20, and at 14,400
- For more than a hundred dollars.


   Minutes of the correction and compression
data - a very useful thing.

   Correction of errors in practice
means that during transmission
data terminal mode itself
modem (it deals with its "iron"), without the help of your 
program will deal with interference in line and not allow a 
failure of symbols, and the appearance of unnecessary.


   Data compression means that
Again, the modem transmission
blocks will be their packaging, of course, saving this time
transmission.


   So I would recommend
buy modems specifically with the protocols, it will cost a few 
dollars more, but will save a lot of time

and nerves in relation to noisy lines.

              ____


   So, what do we have?


   In St. Petersburg for a year already Sergei
Zonova sold the RS-232 and
terminal program under iSDOS external hayes modem.
Speed data exchange with the port
- Up to 9600 baud. Protocol -
X-modem. Program in general is an exact copy vikommovskoy,
and has the same features plus
dialing. Using a modem protocols pleasantly pleasing to the eye 
to the lack of garbage screen and 100% safety of the characters.



   However, I am more sympathetic to
option to connect the internal
hayes'a. Why?


   First internal modem
is cheaper than external (External
has its own power supply and case, so the price of
it somewhat more expensive).

   Second connector
Internal hayes'a do not need
to spend on RS-232 port, so
as an internal modem connected to the computer bus.

   Thirdly you are not limited
9600 baud (author shemki
Connection Michael Kondratyev
used US Robotics 14400).


   Connecting the internal hayes
will cost you three chips and
slot. Policy support for
it develops, and development of its
depends on the number of people, it
uses. While some people, the program can only essentials. In 
the next plans - implementation file

Protocol Z-modem, which is much smarter and more convenient 
X-modem'a; and a few other ideas.


        ________________


   Author wiring diagrams and
iS-DOS software support - Michael Kondratyev,
have access to Fido can send him soap on the address
2:5030 / 362.1

   The author of this article - Vladimir
Larkov, wishing to complement or
challenge the above can
send soap on 2:5030 / 362.2


   In one of the following numbers
ZX-Format to be published
Internal wiring diagram
hayes-modem to the ZX-Spectrum.



  With best wishes, Vladimir.

  St.-Petersburg, 14-Feb-1996
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