Search found 38 matches

by Black_Cat
Sun Jan 13, 2019 11:49 am
Forum: News
Topic: Port system documentation updated
Replies: 33
Views: 2569

Re: Port system documentation updated

It doesn't cause problems for the Eastern machines simply because they don't need compatibility with legacy software accessing those ports in the wrong way. You are mistaken, in exUSSR computers, if possible, compatibility with old software is supported. Given example: Example 1. The demo often use...
by Black_Cat
Sun Jan 13, 2019 3:24 am
Forum: News
Topic: Port system documentation updated
Replies: 33
Views: 2569

Re: Port system documentation updated

The additional address line A16 is used selectively only when justified.
by Black_Cat
Fri Jan 11, 2019 5:24 am
Forum: News
Topic: Port system documentation updated
Replies: 33
Views: 2569

Re: Port system documentation updated

You mentioned two ways of development, and I explained what their difference is - Russians have been developing their computers in accordance with the Altvasser architecture for 30 years, and have no problems with incomplete decoding, while in the West they know nothing about the Altvasser architect...
by Black_Cat
Mon Jan 07, 2019 6:19 pm
Forum: News
Topic: Port system documentation updated
Replies: 33
Views: 2569

Re: Port system documentation updated

It should be remembered that there have been splits in the evolution of the ZX Spectrum and that the ZX Next is a descendant of one of the paths while machines like the Pentagon and ZX Evolution are descendants of another. As a result a solution that is ideal for one may be ideal for the other. The...
by Black_Cat
Fri Dec 28, 2018 5:26 pm
Forum: News
Topic: Port system documentation updated
Replies: 33
Views: 2569

Re: Port system documentation updated

No I can see how it works - it's just something you don't really want to do but if it solves all the port conflicts it might be something that you'd end up having to do for the sw compatibility. I'll come back to this when the pentagon is revisited, or maybe sooner since its percolating now. What e...
by Black_Cat
Mon Dec 24, 2018 9:54 pm
Forum: News
Topic: Port system documentation updated
Replies: 33
Views: 2569

Re: Port system documentation updated

Alcoholics Anonymous, do you need comments on port decoding, or do you understand why the decoding is done this way?
by Black_Cat
Mon Dec 24, 2018 5:50 pm
Forum: News
Topic: Port system documentation updated
Replies: 33
Views: 2569

Re: Port system documentation updated

out(nn),a/in a,(nn) command trap
by Black_Cat
Mon Dec 24, 2018 4:44 am
Forum: News
Topic: Port system documentation updated
Replies: 33
Views: 2569

Re: Port system documentation updated

varmfskii wrote:
Mon Dec 24, 2018 3:08 am
While not in issue with an FPGA version of a Z80, with an actual Z80 how does the hardware determine whether to assert A16 or not?
The out(nn),a/in a,(nn) command trap is used.
by Black_Cat
Mon Dec 24, 2018 1:43 am
Forum: News
Topic: Port system documentation updated
Replies: 33
Views: 2569

Re: Port system documentation updated

Also, I would recommend changing the port decoding: +-+-++--------------------+---------+--------------------------------+ | | ||AAAAA AAAA AAAA AAAA| | | | | ||11111 1100 0000 0000| | | |R|W||65432 1098 7654 3210|Port(hex)|Description | +-+-++--------------------+---------+-------------------------...
by Black_Cat
Sun Dec 23, 2018 4:48 pm
Forum: News
Topic: Port system documentation updated
Replies: 33
Views: 2569

Re: Port system documentation updated

:) Wery well. :) Thus, we have come to understand the need to apply the exUSSR concept of ZX Spectrum port decoding. :) The essence of the exUSSR port decoding concept is to add an additional A16 address to the I/O port address space: A16=0, if out(nn),a/in a,(nn) is not used; A16=1, if out(nn),a/in...