6510 CPU clock question. - Page 1
Forum section: electronics / beginners

author: Unknown
author_rank: Unknown
timestamp: April 09, 2012, 10:04:59 am
content: Hi, In a design which say used the 6510, would the 02 phase out from the CPU be used to tell another part of the system that it's ok to use the bus etc, so it's possible to multiplex and to do perhaps a dram refresh, like on the Commodore 64?Regards

author: SeanB
author_rank: Super Contributor
timestamp: April 09, 2012, 11:00:04 am
content: Read the data sheet ( and look at the Apple ii schematics as well) and you will see this in use.

author: 6502nop
author_rank: Regular Contributor
timestamp: April 09, 2012, 03:05:05 pm
content: You may want to bookmark 6502.org for all things 6500-ish. Designing, coding, and interfacing are all covered, with no apparent animosity towards various manufacturers (as long as it's a 65xx CPU, it's fair game).Also, Quinn Dunki of BlondiHacks (a member here, too!) has an extremely good series covering design and testing.On a personal note, I'd stay clear of DRAM when using a CPU with only 64K of address space. Back in the day, when RAM was astronomically priced, it made sense. Nowadays, you can pick up a couple of 32Kx8 (Cypress CY7C199) or 64Kx8 (UMC UM61512AK) Static RAMs (used for older 386/486 cache) for a couple of dollars. By doing this, you eliminate about a half-dozen timing chips and phase/bus controllers that do nothing but refresh DRAM and slow things down. Using static RAM means just buffering the I/O lines, routing the control lines, and Bob's your uncle (I actually have an Uncle Bob)!Also, make note that the 6510 is a little bit different (okay, it's actually two bytes' difference) from the regular 65xx series. The 6510 has a built-in port, located at address $0001, with the Data Direction Register (DDR) located at $0000. It works just like the 6520, 6522, and 6526 VIA/CIA chips, where you set the DDR, then put/pull the value to/from the port. They did this as a way to address >64K by bank switching, but things didn't quite work out well enough. In fact, Commodore, who bought MOS Technology and re-named it to Commodore Semiconductor Group (CSG), used it only to switch in/out the ROM chips, so that the user could use the underlying RAM for programs (game cartridges could also do this).So, read up at 6502.org about phase timings (and notice how many SBC projects use SRAM, not DRAM!), and head to Western Design to get some NEW 65xx chips that run in the 16MHz range! Awesome!nop

author: Unknown
author_rank: Unknown
timestamp: April 11, 2012, 08:48:51 pm
content: Many thanks for your reply's. I'm quite new and inexperienced at understanding datasheets and at electronics in general but after re-reading the 651x datasheet then reading it again I realized the 6510 and it's 02 pin is different from the 6510-1 variant and I was getting mixed up; so when I hooked my scope up to my commodore 64's 6510; the 01 and 02 lines seemed to follow the timing in the datasheet, ie with a lag in the 02 lineI'm basically trying to understand the logic circuits of the commodore 64 as a chill-out, whilst working on a pottery kiln controller; but I think it's because I fancy a retro 65xx computer project next!Regards