"NOP generator" for 6502-based systems with DIP ROMs - Page 1
Forum section: electronics / general

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: March 25, 2020, 12:29:55 pm
content: At least I hope it is.Now to select resistors.edit: umm, maybe I should explain a bit. This is something I just tossed together in a few minutes to try out OSH Park's "After Dark".This is supposed to replace system ROMs in 6502 systems and will always return the NOP opcode (x0EA) to force the 6502 to step through its address space at half the clock speed.For troubleshooting.

author: KrudyZ
author_rank: Frequent Contributor
timestamp: March 25, 2020, 05:06:21 pm
content: What happens when you reach the end of the ROM select range?Assuming the system has other memory, like RAM, the range select logic would be external and the processor would stop looking at your ROM...

author: NivagSwerdna
author_rank: Super Contributor
timestamp: March 25, 2020, 05:19:16 pm
content: Where did you get the DIP pins from?

author: SiliconWizard
author_rank: Super Contributor
timestamp: March 25, 2020, 05:45:07 pm
content: Quote from: NivagSwerdna on March 25, 2020, 05:19:16 pmI was also going to ask, but they look live salvaged pins from some connectors...

author: SiliconWizard
author_rank: Super Contributor
timestamp: March 25, 2020, 05:46:54 pm
content: Quote from: KrudyZ on March 25, 2020, 05:06:21 pmAs there doesn't seem to be anything active on this, I'm also wondering how it can cohabit with other chips on the same data bus?

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: March 25, 2020, 05:52:00 pm
content: Yeah it's a last resort kinda thing. You remove the other memory on the board or you can remove the decoding logic.The PC rolls over from 0xFFFF to 0x0000 and keeps going.The kind of boards I intend to use this on are all 1980s stuff. 74LS and DIP ROM and RAM.Although with all the 6502s I bought I can just swap the chips.Like I said, I really wanted an excuse to use the After Dark thing.Quote from: NivagSwerdna on March 25, 2020, 05:19:16 pmSigh. I don't remember.Quote from: SiliconWizard on March 25, 2020, 05:45:07 pmNope!

author: edavid
author_rank: Super Contributor
timestamp: March 25, 2020, 06:00:15 pm
content: Matthew D'Asaro used to sell the pins - not sure if he still does, but you could ask.http://www.dasarodesigns.com/product/batten-and-allen-ba3760-dill-leadframe-dip-pcb-edge-clip-pins/

author: NivagSwerdna
author_rank: Super Contributor
timestamp: March 25, 2020, 06:25:50 pm
content: Quote from: edavid on March 25, 2020, 06:00:15 pmSadly he has some conditions, i.e. no re-sale

author: SiliconWizard
author_rank: Super Contributor
timestamp: March 25, 2020, 07:12:17 pm
content: Quote from: Alex Eisenhut on March 25, 2020, 05:52:00 pmOK!Note that you could now design a just slightly fancier one with just an added 3-state buffer (such as 74HCT241) so that you can use it without removing anything else!

author: edavid
author_rank: Super Contributor
timestamp: March 25, 2020, 08:10:29 pm
content: Quote from: NivagSwerdna on March 25, 2020, 06:25:50 pmWhere do you see that?

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: March 25, 2020, 08:35:47 pm
content: Quote from: edavid on March 25, 2020, 08:10:29 pmI think he means re-sell one of his products that uses the pins"Building one of my products yourself (remember: personal use only without my prior consent)"