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Scenergy #01
31 мая 1999 |
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Coding - Driver RAM DISK'a for ZX-Spectrum'128.
Driver RAM Disk'a for the ZX Spectrum 128
1. Instead of joining
It was a very long time ... Or, to be
exact - in the courtyard stood a 1995-th year. As
once in a while, we, like all beginners
Spectrum team worked directly over
many projects, and planned to make
more. Some of these projects
naturally applies to such genres as
game and the demo (including the plans were
notorious Megaball and Paradise Lost).
And that is also quite obvious to
start-up team - we've had problems with
software. In particular, we did not have enough
programs to work with sprites - it
simply not there.
It was then that the idea SpriteLand'a.
At first it was just a bunch of protsedurok
not having not only the public interface, but
did not cumulate. Each of them
simply run out of Zeus'a,
rehearsed, and then the results manually
unloaded by BASIC. Subsequently
(Where such a "convenience" we
sick and tired) wrote the first version
interface (on BASIC'e) and were taken
attempts to assemble it all in a heap.
More - more. We have already become clear that
of "utility for internal use"
This program is gradually grows into something
quite competitive ...
Version 1.0 appeared in October of 1995,
Then, literally within a month
came up to version 1.19. And
version 1.11, even managed to sell Logrosu
for "big money" - $ 100! :)
Apparently, so version 1.11 was the most
widespread, despite some
bugs.
At version 1.19, oddly enough all
decayed ... And the decayed capital -
as much as 2 years:) And this is despite the fact that
there sat a couple of ugly bugs, and
some necessary functions simply
absent.
Resuscitation of the project no matter how SpriteLand
strange happened thanks to the emergence
Project Scenergy, the first issue of which you
currently watching on the screen
your monitor. Was produced significantly
Modified version 1.25, but further
me she had never left. The thing is,
I was planning to publish it in
annex to the zero number Scenergy, but
a number of reasons it was never released.
Now, in the first issue you Scenergy
It starts with two gifts: a new version
SpriteLand'a in the annex, as well as in
As a bonus, this article. :)
"Where the hell was he?" - You ask - "when
What is life SpriteLand'a,
when the article is something about the RAM Disk? ". My answer:
The fact is that during development
SpriteLand'a created two very
useful things: a driver and RAM Disk'a
interface library. The time has come, and
Now I want to publish their source code
for use throughout the Spectrum scene.
It is always easier and more enjoyable
use to design their programs
ready, the organized and well
documented source code, rather than
try for the umpteenth time to reinvent the wheel.
That is why the pages I Scenergy
I would like to begin publishing the different source
texts. I hope that experienced coders
support me in this endeavor - because of
this will all just good! Not for nothing
on all other platforms are written in a heap
Articles with the descriptions of the algorithms
published sources pile - it is very
contributes to the development platform. That's right
learn from this good tradition!
2. A few general words
So what we have today? In this
article you will find a complete description of the driver
RAM Disk'a and annex - itself the source
format TASM v3.0.
All (c) at the source and description
belong to me - Flying / DR. Wherefore, I,
as the copyright holder, authorize its
free use for any purpose.
Also allow to patch the source with
to its completion or alteration to your
needs. The only condition - to save
copyrights.
This driver was created specifically for
SpriteLand'a. Date of last revision:
10/25/1995 (antiquity of which:)). When
establishment used TASM v3.0 (c)
RST7/CBS and STS v2.6 (c) Stalker, for which they
thank you so much!
I hasten to note that I have not finished the
driver specifically for publication - it
it is in the form in which it stands in
SpriteLand'e. This is partly because my
laziness thoroughly understand the source
written by more than 3 years ago, and partly
the fact that I do not want to go into full
work program. About 100% bug-free
this driver I can speak
Based on what has been 3 years he
works in SpriteLand'e and for all this time
no bugs in it is not noticed.
Again due to my laziness in the text
source code remains a bit vague
description of the driver features a slightly
clumsy English (because it is not TASM
supports Russian characters and Glory
God! :))
3. Characteristics of drivers
Utility: This program
is a driver for the RAM Disk'a
ZX Spectrum 128.
Specifications Driver:
- Maximum number of files on the RAM
Disk'e: 256
- File size: 1 .. 65535 bytes.
- The maximum amount of disk: 64kb
(More on this below)
- Operations are supported:
- Read
- Record
- Remove
- Rename
- Optimization of space RAM Disk'a
- The principle of organization: a-la TR-DOS, but
memory is not divided into sectors
minimum unit - 1 bytes.
- How it works: a-la TR-DOS. Ie through
entry point to the transfer function number
and the parameters in registers.
- Memory requirements:
- The driver itself: 1588 bytes
- Buffer for the operation: 256 bytes
- Catalog of RAM Disk'a: 256 * 6 = 1536 bytes
- The rest of the page based memory can be
used under the RAM disk.
Directory can be paged in
memory, the driver itself and a buffer should
stay below # C000.
All operations with data on the RAM Disk'e
made through the buffer. This allows
remove all restrictions on the address
location data for read / write.
The buffer size can be varied at
compilation, however, should remember that
too small buffer size will lead to
general slowing down procedures RAM
Disk'a.
It should be noted that in contrast to TR-DOS
files on the RAM Disk'e not have a name -
only the number, which, in essence, is
file name and is used in all
disk operations.
4. Driver Features
All work with the driver of RAM Disk'a
performed through a single point of entry.
Number of the calling function and the necessary
parameters are passed through registers.
The general format of the call driver functions:
LD A, <function number>
CALL RAMDRV
Output for all functions of the contents
register reflects the current state of RAM
Disk'a:
- Flag CY indicates success or
ended with the driver.
CY = 0 - everything is OK
CY = 1 - error. In this case, A
would be an error code (see below)
- Register B contains a number of
used descriptors. In general,
If it is not equal to the number of files
on the RAM as Disk'e Deleted files too
occupy descriptors before will
Optimization space
RAM Disk'a.
- Register C contains a number of
free memory pages.
- Register of HL contains the number of
free memory currently in use
page. Thus as registers
C and HL can estimate the total number of
free memory on RAM Disk'e.
Driver functions:
# 00 - driver initialization RAM Disk'a.
Directory is cleaned and
initialize all internal
variables. This function must be
call before you start working with RAM
Disk'om.
Parameters:
No
# 01 - Reading a file from the RAM Disk'a in memory.
Reading is made to any address
in memory, but only the main
computer memory! Read / write
Page memory driver does not know how!
Parameters:
HL - Address of buffer in memory to be
reads.
DE - The size of the read block. If DE = 0
the size of the block will be taken from
descriptor file in the directory.
B - Number of retrieved files.
Possible errors:
# 03 - 'Object is non exist'. File with the same
number on the RAM Disk'e absent.
# 02 - Writing to a file on the RAM Disk.
Recording from any address
in memory, but only from the main
computer memory! Read / write
Page memory driver does not know how!
Parameters:
HL - Address of buffer in memory, which will be
recorded on the RAM Disk.
DE - The size of the recording unit.
B - Number of the recording file.
Possible errors:
# 01 - 'No free ram disk space' Out
space to write the file to
RAM Disk. Worth a try
free up space, making the optimization
RAM space Disk'a.
# 02 - 'Catalogue overflow'. All the descriptors
Directory RAM Disk'a busy. Worth
try to free the descriptors
occupied by deleted files, making
optimization space RAM Disk'a.
# 05 - 'Object is already exist'. File with
this number is already in RAM Disk'e
# 03 - Deleting a file from the RAM Disk'a.
Parameters:
B - Number of deleted files.
Possible errors:
# 03 - 'Object is non exist'. File with the same
number on the RAM Disk'e absent.
# 04 - Rename the file.
Parameters:
B - Old file number.
C - A new file number.
Possible errors:
# 05 - 'Object is already exist'. File with
this number is already in RAM Disk'e
# 05 - Optimize RAM Space Disk'a
This function is similar to the operation
MOVE in TR-DOS. As a rule, cause
it should be in case of errors
'No free ram disk space' or
'Catalogue overflow' when trying to
record file as it may
frees disk space and
descriptors employed remote
files.
For example, in SpriteLand'e call this
function is built into the procedure
Driver error handling RAM Disk'a
and after receiving appropriate
error at first tries to
defragment the RAM space
Disk'a, then re-done
attempt to write the file, and only
case of repeated failures is given
error message.
Parameters:
None.
Possible errors:
None.
# 06 - Getting information about the current
state RAM Disk'a.
Actually, this function is purely
formal because return it
data and so returned to each
accessing RAM Disk'u. But sometimes
it is useful to learn about the current
state RAM Disk'a nothing in this
not doing.
Parameters:
None.
Possible errors:
None.
# 07 - Getting information about the file.
Parameters:
B - File Number.
Return values:
B - File Number.
C - Number of page on which
beginning of the file is located. If
C = # FF, then the file does not exist
on the disk.
HL - Address to which the file resides
on the RAM Disk'e. In principle, data
Registers C and HL can get
to file data directly to
Disk'e RAM, but I do not do it
advise as no one can
guarantee that the file
entirely located in one page
memory.
DE - The length of the file.
Possible errors:
None.
5. Error messages.
These error messages are returned
A case in every time you call the driver
RAM Disk'a. If the error code is different from
# 00 - CY flag is set as a sign
erroneous conclusion.
# 00 - 'No errors'. All OK.
# 01 - 'No free ram disk space' Out
space to write the file to
RAM Disk. Worth a try
free up space, making the optimization
RAM space Disk'a.
# 02 - 'Catalogue overflow'. All elements in
catalog RAM Disk'a busy. Worth
try to free the descriptors
occupied by deleted files, making
optimization space RAM Disk'a.
# 03 - 'Object is non exist'. File with the same
number on the RAM Disk'e absent.
# 04 - 'Illegal function number'. Function
with this number is not in
driver.
# 05 - 'Object is already exist'. File with
this number is already in RAM Disk'e
6. The directory structure RAM Disk'a
The directory structure Disk'a RAM:
+0 [Byte] File Number.
+1 [Byte] starting page number or
# FF if this descriptor
free.
+2 [Word] Address of the beginning of the file in memory.
+4 [Word] size.
Data from (a) and (2) form a complete
pointer to the beginning of the file in the space
RAM Disk'a.
Number of pages - the logical (# 00 .. # FE).
Physical page number is taken from
Table RAMPAGE (see below)
7. Description of the internal variables
Strictly speaking, the source is sufficiently
well commented (though in English
dubious quality:)), so here
I will describe only the most important variables
and function.
EQUS:
CATLEN EQU 6
The size of each directory entry RAM
Disk'a. At the moment, is 6 bytes
thus, the entire directory is:
6 * 256 = # 600 = 1536 bytes.
Postscript to this variable in the source
states that when resizing
directory entry to be rewritten
multiplication CATLEN the procedure GETPADR
so be aware! :)
CAT EQU # C000
Directory location in memory. As I
have already said - it can be located
anywhere (even on pages where he
sits in SpriteLand'e). More details
See description on CATPAGE and
procedures SETCATP.
BUFLEN EQU 256
The buffer size for data exchange between
Disk'om RAM and main memory. In
original form is located in the body
driver, but can be located on
any address below # C000.
MAXFUNC EQU 7
The number of functions supported
Driver RAM Disk'a. Need for
validation function number.
RAMPORT EQU # 7FFD
Port number of switching pages.
Originally intended to do
support for extended memory (as
below), but before the end of this idea has not
has been implemented ...
Variables
PAGES DEFB 4
Number of memory pages used
a RAM Disk. In principle, the RAM size
disk'a not limited to 64KB, but because
in SpriteLand'e (where I got this
source) of free memory left
only 64kb - and here, respectively,
is the number 4. An increase in the size
RAM disk'a - below.
MAINRAM DEFB # 10
Number of pages included by default
as the main computer memory.
I will explain a bit: The driver actually can
work (read / write) with only
the main computer memory, which
As is known, consists of a 5-st, 2 nd, and
another one (any) included in the page
Articles with the descriptions of algorithms, procedures,
koderskih various tricks to enable
improve the performance of programs ... And in
appendix, we will see high-quality
source that will be useful not
only novice coders.
Dreaming ... :) Let's see - can my
dreams come true ...
Address # C000-# FFFF. So, the number of the
pages and must be set in this
variable. The page number should be
Physics!
By the way, if you change this number of the country
particle - you can read / write and other
pages of memory:)
CATPAGE DEFB # 11
Page number in which the
Catalog RAM Disk'a. It remains of
SpriteLand'a in which directory RAM
Disk'a lies in the paged memory. Number
Pages must be physical!
RAMPAGE DEFB # 13, # 14, # 16, # 17
This table lists the physical
number of pages allocated for RAM Disk.
Their number is specified in the variable
PAGES.
BUFFER DEFS BUFLEN
Buffer for data exchange. If desired,
can be rearranged to another location.
FUNCT
DEFW INIT
DEFW READ
DEFW WRITE
DEFW ERASE
DEFW RENAME
DEFW MOVE
DEFW SYSINFO
DEFW OBJINFO
This is a table of pointers to procedures
implement the corresponding functions
Driver RAM Disk'a. Address Procedure
selected by the feature number.
Procedure, I will not describe here - those
who need it, will be able to deal with
them yourself. The more so because each procedure
in the source file contains a comment with a brief
description and listing of its input
parameters.
8. Prospects.
Naturally, the first thing you want
to do with this driver - make it
work with different top memory
computer models.
Getting to write this article, I have
just looked at the source, and found that
obstacles to this no! :) How
Still cool, I wrote the program 3 years
ago! :) Apparently affected by training
3 rd POVT'a course at the university.
In general the only thing that interferes directly
immediately begin using this driver with
upper memory - no proper
switcher pages of upper memory.
What should be done to make it work?
1) Insert the procedure for switching
page top of memory instead of the procedure
CHPAGE. At the entrance of this procedure
transferred to the logical page number
RAM Memory Disk'a. This procedure should
take a physical page number from the table
RAMPAGE and turn it on. All registers must
be preserved.
2) A remake of procedure
SETMRAM and SETCATP so that they included
pages respectively of main memory and
Catalog RAM Disk'a. (For more details see
descriptions of variables and MAINRAM CATPAGE).
Everything! :)
Thus, you will receive the full
working RAM Disk with a maximum capacity
# FE * # 4000 = 4,161,536 bytes, or nearly 4Mb!
In addition, it would be nice to add another
functions in addition to the existing. Make
it is also easy:
1) Write a new function driver. All
procedures for dealing with low-level RAM
Disk'om at the start of the driver.
2) Add a pointer to the table
FUNCT.
3) Change the number of functions in MAXFUNC.
And yet - the function will be part of the driver.
9. Afterword
Hopefully, this driver useful to you.
Its really easy to use
when writing a number of programs (SpriteLand'a,
for example:)).
I also hope that other coders
support my initiative, and in the pages
our journal, we see good
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