Z280 to Z80 adapter revisit

Page 6/6
1 | 2 | 3 | 4 | 5 |

By Edevaldo

Expert (92)

Edevaldo's picture

05-12-2018, 17:22

I need to apologize to Lintweaker for taking his topic "off-topic".

By Grauw

Enlighted (7525)

Grauw's picture

05-12-2018, 19:33

I just took it back on-topic to the Z280, don’t worry Smile.

Okay, this is interesting… the R800 MULUB A,r and MULUW instructions have the same opcode as the Z280’s MULTU A,r and MULTUW HL,rr instructions. I’m really gonna have to try some stuff now…

Edit: Okay, so far of all the Z280 opcodes I’ve tried, none seem to have any effect. Would’ve been too good to be true if some of them worked I guess Smile. It’s got some great additions to the instruction set. But anyway, R800 compatible at least (see above), so could be a good replacement. And if configured right, I think it can access the bus with MSX standard timing.

By PingPong

Prophet (3147)

PingPong's picture

05-12-2018, 19:51

about FPGA - V99x8 emulation timings details are not so known.
Expecially for V9958 ( V9938 had some detailed timings done some years ago via a digital analizer) there is not much under the day light. For example no one knows about the timings of the WAIT line, nor in what specific situations is activated and what is the delay when this line become active.
Plus it is suspected that the VRAM bus access timings may depend on the values of the horizontal scroll register but no one knows about.....

By Grauw

Enlighted (7525)

Grauw's picture

05-12-2018, 23:59

https://www.msx.org/wiki/R800_Programming#Changed_instructions

Quote:

Undocumented Z80-operation "SLL" have been replaced with another undocumented instruction similar to "TEST" of the Z280

I tried this, on R800 this opcode (CB 30-37) seems identical to SLA.

(Which actually is a correct implementation for SLL, the Z80 does not do a logical left shift.)

Goes to show there are a lot of myths about the R800 undocumented opcodes that people just repeat to each other without verifying by testing :). Also the Z280 does not have a “TEST” nor a “TST” instruction. On Z280 this opcode is used for “TSET”, but it’s very different from what the R800 exhibits.

By erpirao

Paladin (815)

erpirao's picture

07-12-2018, 15:15

Grauw wrote:

https://www.msx.org/wiki/R800_Programming#Changed_instructions

Quote:

Undocumented Z80-operation "SLL" have been replaced with another undocumented instruction similar to "TEST" of the Z280

I tried this, on R800 this opcode (CB 30-37) seems identical to SLA.

(Which actually is a correct implementation for SLL, the Z80 does not do a logical left shift.)

Goes to show there are a lot of myths about the R800 undocumented opcodes that people just repeat to each other without verifying by testing :). Also the Z280 does not have a “TEST” nor a “TST” instruction. On Z280 this opcode is used for “TSET”, but it’s very different from what the R800 exhibits.

I am reading the thread that you have opened comparing the r800 and z800 / z280, and, without having any idea of programming or hardware, I am looking very interesting.

By АIеks

Expert (100)

АIеks's picture

07-12-2018, 20:04

АIеks wrote:

Everything is real-MSX-EXT. z280 7?

ProtoModule CPU Z280.

By lintweaker

Expert (99)

lintweaker's picture

07-12-2018, 21:38

АIеks wrote:
АIеks wrote:

Everything is real-MSX-EXT. z280 7?

ProtoModule CPU Z280.

Nice solution for setting the bootup bus timing parameters!

Any reason not to use oscillators for the clocks?

Page 6/6
1 | 2 | 3 | 4 | 5 |
My MSX profile