I think the Spectrum Emulator Card is one of the most awaited hw for the Enterprise in Hungary.
When the user bought their Enterprise computers, there were only few programs in the shops. But the advertisments said: "the Spectrum Emulator is coming, with this, you can play hundreds of Spectrum games".
Users waiting, Emulator not coming... only articles, why not... but promising shortly coming...
After long time... yes! the Emulator in the shops!
But many users say: this is a disappointment...
The original version of the Emulator has lots of bugs. And the users did not understand why. The developers had so mcuh time...
And the developer company ('a' Studio) did not respond to the users complains.

What are the bugs?
-With the Emulator, you can use your Enterprise as Spectrum. To return to the EP mode you needed to unplug the Emulator. This is not good for the connectors...
-You can't use the Emulator with EXDOS. But who have disks, they do not want to hear tape sounds any more
-Joysticks cannot be used (Internal or External) in games.
-Keyboard emulation has lots of bugs, some keys are often dead, or one key is detected as two...
-If the program uses Interrupt Mode, it will hang up... Many games the IM2 is used...
-FLASH attribute is absolutely not emulated, this cause: you cannot see the cursor in a lot of programs
 

The original Emulator has version 3.5 ROM

The operation of the Emulator is a brilliant idea!

The logical circuits in the board, verifying all bus operation. And when detecting Spectrum type operations, generating NMI.
The NMI handler in the ROM, reading the ports of the board, and select which function needed to emulatad, and run the suitable emulation routine.
The ports of the board (40H-44H), contains the data of the Address and Data Bus and some additional information, at the NMI generating moment. 40H: A15-A8, 41H:A7-A0, 42H: D7-D0 (bits are mixed), 43H: bit7=1 when memory operations, 0 when I/O operations
Spectrum type operations:
-Read or write the FEH ports. Read used by keyboard scan, write for generating sound, and setting the border color.
-write to the attributom area of the screen, this is phisicaly at the segment FEH, from 1800H-1AFFH

About the keyboard bug of the original version:
In the ZX Spectrum using the following Z80 properties: when reading from I/O ports, the upper 8 bit of the address bus contains the value of the  A or the B register. With this value can be selected which keyboard line needed to reading.
The PCB have a bug, A15 not connected to U9...
Programer bugs: at the Enterprise the A15 and A14 not directly from the Z80! The Z80 A14-15 used by the DAVE for memory paging. The A15-14 at the bus port from the DAVE, and depends of the currently used segments!
In my new program I use four segments which have unique bit combination at the lowest two bits. This bits will coming to the bus as A15-14.
After the PCB is corrected, and with the new program, the keyboard emulation works correctly.

Because the NMI generation are not EXOS compatibe, needed to put a ON/OFF switch to a NMI line. When starting the 4.0 version of program, it is say turn on emulator. And when you want to exit, turn off the emulator, and press reset. After this you exit to BASIC (or the program where you called the emulator)

Thanks for the information,  I am currently looking at the ISS2
schematic but it may well be worth me moving over to the ISS3
and go from there.

regards

Russ P.
 

I am looking at using an 84pin PLD so I am only using about 60%
of the availble connections.

The possibility of upgrading later will be available as long as we
do not use all of the pins.

The other option would be to use a bigger device later, depending
on what was required.

Russ.

Z,

Sorry about the delay in everything but I am now looking at the Spectrum Emulator again.
The hardware engineer who was designing the new board has moved on so I am
starting to get it sorted myself.

Question:  Have you looked at adding a ROM port to the Spectrum Emulator?  I was wondering
if it was possible to play the ROM cartridges.........

Russ.

Just to let you know that the Spectrum Emulator hardware
design is currently being finished off   

This is going to consist of a single CPLD and a PROM.

Have had major issues getting the hardware design sorted as
engineers here are hard to get time from, but we are getting
there.....

Regards

Russ P.
 

Hi Russ!

This is good news!

how many boards will you make?

p.s. the QWERTY keyboard is still working well - thanks again!

Z,  wa are using the Issue 2 design for the moment.

Ok, but when using this version, then needed to put switch on a NMI line.
ISS3 is a more comfortable, because it's can be switched on/off by the sw. (The hw bug of the original emulator fixed in the ISS3)

On the ISS3 circuit diagram you are using 27512 PROM, is there a reason for this?

More space for future expansions. Currently not important. (But you can use the free 32K for any ROM programs, if you use EXOS 2.3)

Can a 27256 be used in plac of this, as I have a surplus of these PROMs?

Yes 27256 can be used at 27512 socket.