Scrap Metal - Emulation of the 1818VG93 drive controller.

Emulation 1818VG93
Alone Coder 

 There are as many as 5 ways to stop
 disk rotation in the drive:
 1. Apply to the RESET input of the microcircuit─
 we are 1818VG93 logical zero.
 2. Write MIC─ to the command register
 circuit diagram 1818VG93 command.
 3. Generate an IP mic at the input─
 circuits 1818VG93 several pulses─
 owls.
 4. Remove the disk from the drive.
 5. Turn off the power.
 All methods except the last
 two, work on all controllers
 Beta Disk interface.
 fkO

   Computer Pentagon 2.666 (authorKing of
Evil) is a rather unusual device. Yes─ 
but if you don’t pay attention to the neighborhood with─
Soviet microcircuit K561LN2 with peripheral
controller on ARM architecture or on─
inscription"DEATH TO NATO", which can
to export it to some countries :)
   On the one hand, Pentagon 2.666 is similar
on organizing the devboard, since the village
troen on FPGA. On the other hand, this is not a development board,
since there are no other firmwares except
Spectrum, not planned.  With one
On the other hand, Pentagon 2.666 has been around for a long time.
On the other hand, many will only learn about him this time─
hour
   Now, like ZX Evolution, Pentagon
2.666 compatible with classic clones 
Pentagon and ATM Turbo 2+, with support for races─ 
extended memory according to the "ATMZ" standard (ports
#x7F7 and#BF ) and as a bonus - also expanded─ 
noy palette from DDp. Unfortunately, support
There are no proprietary timings, but over time it
may also appear. Especially if someone
decides to mass produce the computer...

   The story went like this. Development of the device─
new part began in 2007 in the footsteps
Pentagon 102ХSL v2.2 (one time compo─ 
car on DiHalt and Chaos Constructions) and
Z-Controller devices from the same author.
The goal was to significantly speed up the computer
and switch to available peripherals (PS/2
keyboard and mouse, SD card), notlosing owls─
capacity with devices for ZX-BUS. It was
two options are planned: 4-layer with real─
processor Z80 (2.666) and 2-layer with
processor inside the FPGA (2.6bbLE). Version
2.666 appeared in the summer of 2008, 2.6bbLE - 
in the summer of 2009. Both boards were shown on
DiHalt 2009. Demonstrated at 28 MHz 
Wolfenstein 2004 game.
   Initially, it was unclear whether it would work out before─
achieve full compatibility with a processor
in FPGA. It turned out that it was real. Spezia─
the flax modified T80 core did not show from─
lichy on any program. Low-tech─
The new 4-layer version was discarded in
I use 2-layer.

   It would seem to be a success. But before the transformation
boards into the product was a big obstacle
- how to download programs without actually having─
drive, from an SD card.
   The board has 2 MB of RAM (under consideration
question of expansion to4 MB), but does not have
ROM available to the processor (i.e.
for FPGA). Between FPGA and ARM thin one-bi─
a secure interface through which data and
bootstrap data and commands -
data for peripherals, and even text ec─
debugger run (which runs on ARM). B
As a result, the ROM is implemented through RAM. From 2 MB
RAM, or rather, from the top megabyte -64K
(in the future and more) allocated for ROM
and is write protected. The rest of this is top─
The ramdisk occupies one megabyte.
   What's in these64K? 48K, 128K, TR-DOS 6.xx
(with ramdisk) - this is understandable. Reset process─
found in Mr Gluk Reset Service - this is also
16K. To upload images to ramdisk in
Mr Gluk Reset Service added one more 
line - calling the Fatall copier (author
- Savelij13). It is transferred in the definition─
RAM page at startup.

   Not all programs work with ram─
disk. To do this you need to use the call
#3D13. No turboloaders or bootloaders─
kov with music. Or is it still possible?
   There are ROM firmwares that
or otherwise intercept calls using
used in turboloaders. Some of them
have additional branches in #2A53 or
other procedures (vTR-DOS and
Evo DOS), some using additional─ 
bad hardware when trying to access ports
transfer control to the shadow ROM (circuit from
JtN ). Both there and there have one drawback - pro─ 
the processor executes additional commands,
that is, compatibility with exotic sofa─
volume is not complete.
   Full compatibility is obtained if
emulate with iron a bunch of 1818VG93 (cont─
disk drive roller, "VGshka") +drive. And
this was also done.

   It works like this.

   Using direct memory access rea─
read-write access to cells is lost
RAM, bypassing the processor. In a certain mode
the circuit can read data from the cell, do
them available through port#7F and go
to the next address. In another mode nao─
borot - write data to a cell when writing
to port#7F and also move on to the next one
address. This is the main part of the pro─ interface
processor - 1818VG93 - disk drive.
   For other drive controller ports
the corresponding registers are highlighted, they can be
read and write. These are sector registers, up to─
horns, commands and status. Also implemented
system register of the beta disk (its main
purpose - it controls the "disk" side
you", that is, the drive head number).
The contents of all these registers, as well as
registers of the drive model, you can view─
dig in the built-in debugger.
   How should a VGshka behave? VGshka at─
Accepts commands and returns status. VGshka
communicates with the drive (more precisely, with its mode─
I pour), moving his “head”. VGshka has op─
limited delays during positioning.
From the drive (more precisely, its model) VGshka at─
accepts signals"tpekO" and "index impu─
ls" and returns them in status.
 Next, the question concerns the drive. Tracks-
disk sectors are mapped to memory in
in accordance with the location of the frames─
disk. When the drive is "positioned" to
such and such a path, such and such a “goal” was chosen
ka" and the command is given to read such and such a sector,
the reading address is formed from these three elements─
mektov.

 Of course, a real disk drive has a certain
Line speed of rotation and access to data─
nym. A real floppy disk has a certain
location of sectors (this or that). Need
some delays that are yet to come
select.
 But the software is already working. The step has been taken. Case
for support from the community. Doku─
mentation for the production of the board freely
available.
 Write:KingOfEvilyandex/ru