SofiST wrote:Original idea was to hit 2 flies at once: getting PAL logics, so can repair now very old ICD adapters. + making replicas.
Now we are smarter, for sure. I think at moment that doing AdSCSI ST replica now is not the best idea. It is not so fast as could be - at least not my exemplar. It is possible to do faster ACSI-SCSI adapter with some GALs or with CPLD. But question is, is it now interesting in era of Flash cards ?
True and this is why I did not push too hard on Jookie However I still have many SCSI devices (HD, CD/DVD, Tape) and I wanted to use them. Now that I have been able to buy 2 AdSCSI boards I feel safe on the subject. But it took me about 5 years to get them at reasonable price
DrCoolZic: I think that you are wrong considering usage of 3-state by ICD. It is elementary if want that your device/design work together with some other on ACSI bus. Data lines of inactive device must be in high-Z state. And regular bidirectional drivers all have that state. The problems (device conflicts) appear usually with IDs. If IDs are not problem, then inperfect signal decodings, noise, short glitches are culprits. Or overloaded bus/lines.
I did not want to go into details but here are my thoughts:
The Satan/UltraSatan uses the ASCI/DMA bus by connecting themselves in parallel (if you prefer Y connection). Therefore on idle everybody is listening and when selected (after address decode) only one device will be "on the bus" while other stay 3-states.
Atari original devices uses daisy chaining: one device input is connected to previous device output. Between input and output connector of each devices you find a bidir-TS LS245 type buffer (see daisy chaining devices section of page 15 of ASCI/DMA integration guide). In idle mode direction is set from in to out and no TS. So data goes from DMA to all devices. Now lets assume we have three devices and that device two has been selected through a command of the DMA. In that case device three must be set in TS so that data from device 2 drive the bus between 3 and 2 (through LS240 with ICD adapter). But device 1 is not set in TS so that data from device 2 can be transfered to DMA. This is a short explanation for more detail see page 42-48 of the guide that describe in details a ASCI adapter and in particular the SCD SIO and SMSG signals.
NOTE: This explain why YOU MUST PLACE your Satan/UltraSatan device at the END of a daisy chain using Atari ASCI devices.
I hope this make more sense, and control logic is not not difficult to do. Again original spec is for up to 4 controllers daisy chained (page 9 & 14), and buffered with LS244 or equivalent (page 15).