Search found 95 matches

by keli
Mon Oct 16, 2017 11:00 pm
Forum: HARDWARE DISCUSSIONS
Topic: ST SHIFTER operation ?
Replies: 94
Views: 15039

Re: ST SHIFTER operation ?

@ troed (or anyone).. What was the talks about the shifter wake states thing a while ago ? While we are digging around internally, we could see exactly whats going on with the logic to upset such things.. Though my first guess is the 4 banks of 16 bit shifters do not have a reset, so pot luck which...
by keli
Mon Oct 16, 2017 10:57 pm
Forum: HARDWARE DISCUSSIONS
Topic: ST SHIFTER operation ?
Replies: 94
Views: 15039

Re: ST SHIFTER operation ?

In addition to the speed of the screen data coming in, without additional address pins you'll have a problem programming the extra palette registers required for more than 16 colours on screen at the same time. Another option is to use the unused fourth bit in each RGB nibble in the existing colour ...
by keli
Mon Oct 16, 2017 4:33 pm
Forum: HARDWARE DISCUSSIONS
Topic: ST SHIFTER operation ?
Replies: 94
Views: 15039

Re: ST SHIFTER operation ?

So it would be like this.. shifter2.png So each 16 bit bank is connected directly to the MMU databus.. And which bank is selected is based on a one of four counter, which is clocked on the load line.. You will not be shifting 64 times. Each register in the bank will get shifted in parallel, so only...
by keli
Mon Oct 16, 2017 4:10 pm
Forum: HARDWARE DISCUSSIONS
Topic: ST SHIFTER operation ?
Replies: 94
Views: 15039

Re: ST SHIFTER operation ?

There must be some banks swapping going on here.. Because we have 4 banks of 16-bit shift registers, but of course we cannot load anything into those as we need all four words can only come one word at a time. So like you say we probably do need eight banks of registers.. So by default banks zero i...
by keli
Mon Oct 16, 2017 3:48 pm
Forum: HARDWARE DISCUSSIONS
Topic: ST SHIFTER operation ?
Replies: 94
Views: 15039

Re: ST SHIFTER operation ?

I could probably do with a actual example of what data is in each word.. Single bit in each word can be one or zero, four times over for planes means basically 4 bits to select one of the colour palette registers (0-15). So we actually have steam bits per word, so I assume these 16 bits relate to 1...
by keli
Mon Oct 16, 2017 3:43 pm
Forum: HARDWARE DISCUSSIONS
Topic: ST SHIFTER operation ?
Replies: 94
Views: 15039

Re: ST SHIFTER operation ?

You'd probably need 8 of them. 4 for the data currently being loaded from memory and the other 4 for the data being shifted out to the screen. Possible yes. I was thinking with a 64bit shifter register, that 16bits would get shifted out, then the top bank of 16bits (which would have been shifter to...
by keli
Mon Oct 16, 2017 8:03 am
Forum: HARDWARE DISCUSSIONS
Topic: ST SHIFTER operation ?
Replies: 94
Views: 15039

Re: ST SHIFTER operation ?

OK, so we need 4x 16bit shifters. Assume this 16bit data is read consecutively from RAM ? Such as , 16bit plane 1, then 16bit plane2.. etc That would indeed greatly complicate things :roll: You'd probably need 8 of them. 4 for the data currently being loaded from memory and the other 4 for the data...
by keli
Sun Oct 15, 2017 6:26 pm
Forum: HARDWARE DISCUSSIONS
Topic: ST SHIFTER operation ?
Replies: 94
Views: 15039

Re: ST SHIFTER operation ?

OK, so we have 16 palette registers and resolution register. Though what is the decision to output the data to the RGB ports or store values in a register? One address range must be to latch the video data, others for palette data. As far as I understand, the video data are latched when the /LOAD i...
by keli
Sun Oct 15, 2017 3:00 pm
Forum: HARDWARE DISCUSSIONS
Topic: ST SHIFTER operation ?
Replies: 94
Views: 15039

Re: ST SHIFTER operation ?

It also has to map the palette index for each pixel to the rgb values stored in the palette registers. I assume the 5 address lines are also for updating the palette registers. 16 palette entries require four address lines just for addressing them. (Mapped via FF8240-FF825E, or 0xxxx) The resolution...
by keli
Sun Oct 08, 2017 7:58 am
Forum: HARDWARE ISSUES
Topic: SCART to HDMI converter
Replies: 7
Views: 2323

Re: SCART to HDMI converter

After switching out resistors and adding caps to my cable without luck I finally opened up the converter. Turns out the pins for red, green, and blue are not connected to anything. I could find three short traces that ended in unpopulated headers for resistors, so there was no electrical connection....

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