TRS-80 Color Computer Cartridge Signals (SCS, CTS, SLENB)

[@carlossantiago4845]

SLENB disables the decoding of the CTS, SCS, and ROM. This effectively disables any ROM access and selection of devices at addresses FF40-FF5F. It allows you to perform the full decoding of any additional hardware and roms added to the CoCo. Effectively, anything you insert into the cartridge port will need to provide the decoding and rom code for the system.

[@carlossantiago4845]

To take control of the bus you need more that just pulling SLENB low. This just disables the decoding of address. It does not force the CPU into any state but it can cause issues if the rom is disabled. The proper way to take over the bus is with the HALT or AVMA signals. However, the VMA signal is not available on the cartridge port. Using Halt allows add-in board or cart to take over the bus. Doing DMA (direct memory access) the AVMA indicates the 68E09 will the bus back there is a limitation of 16 cycles before this happens. The 6809 is a dynamic architecture and it's registers must be refreshed periodically.

[@nowhereman999]

These CoCo videos are amazing, you do such a great job explaining the hardware. I've done lots of programming on the CoCo and understand quite a bit of it on the software level buts it's so cool to finally understand how the hardware actually works. That logic analyzer is wicked! I'd love a video explaining the PIA chips in detail on the CoCo. Thanks again for making these videos

[@RetroLogicLaboratory]

Hey thanks for the kind note, sorry for the late reply I've been moving this month. I like the idea of the PIA video, maybe I'll put one together!

[@Jenny_Digital]

First video I've seen you put out there in a while. I enjoyed this one! By the way, I really reccomend smaller easyhooks on chips as I've fried a couple when they touch neighbouring legs. If you've seen the sort that came with the Tektronix 308 you'll know the sort I mean.

[@bryannichols7843]

Cool gear and great vid! Thanks for sharing!

[@lindnertim]

A released cartridge that uses SLENB* is the MOOH cartridge. It provides a CoCo 3 compatible MMU (and SD Card storage) to Dragon and CoCo 1/2 computers. tormod.me/mooh.html

[@luis46coco]

Hello, very interesting, I would like to manually translate this video into Spanish, I have already done it several times for 8bit guy but youtube does not let me, apparently you must authorize the translation by the community to be able to translate it, I hope I can afford to do it, and Thank you very much for the video.