QL expansion serial card...

[Dave]

WANTED: QL expansion port serial card.

Based on any halfway modern UART eg: 16552, 26C92, etc. Something newer than the 6850 ACIA. Must have driver in EPROM.

Will pay exorbitant, extortionate price for working unit or above fair price for non-working but complete unit.

[Derek_Stewart]

Hi Dave,

There was a Fast Serial Port inteface designed by Terry Harman, software was written by Phil Borman.

The design files are on the QL Homepage.

I suppose the interface could be built. Eould you be interested in a completed interface.

[duncan]

Hi

There is also the superHermes board, up to 6 serial ports, & compatible with original QL motherboard and Aurora.

Duncan

[Dave]

Hi Dave,

There was a Fast Serial Port inteface designed by Terry Harman, software was written by Phil Borman.

The design files are on the QL Homepage.

I suppose the interface could be built. Would you be interested in a completed interface.

I looked at that but didn't find the ROM image - thank you for pointing me to it. I tried months ago and wasn't able to extract a usable image from the PCL file, but I could tell enough to see it looked like it was based around the 6402. There aren't any other ICs that offer an upgrade path from the 6402, which was the last of the 80s-early 90s style of UARTs like the 6850 I'm trying to get away from. I'm trying to provide 2 or 4 ports (2 ext plus internal use) and looking to get up into the 1.5MB/sec area with decent sized FIFOs so the service requirement by SMSQ/QDOS is low. Don't get me wrong - the 6402 is capable of going quite fast. It just really limits future possibilities.

I guess this means there isn't a 68681-type interface out there at all

Thank you for offering to build one.

[Dave]

Hi

There is also the superHermes board, up to 6 serial ports, & compatible with original QL motherboard and Aurora.

Duncan

The SuperHermes board still sends serial communication through the 8302 using a slow serial link, which is the bottleneck I am engineering away. Anything going through that connection will top out at around 19,600 baud. There is a little bit of headroom on that, but the next "official" serial speed is faster than the link.

To expand on that, the link can support something close to a theoretical 100kbps if the OS is single-tasking, but around 25-28 kbps if the OS is multitasking and polls less often. Microdrive access can use all that speed, but a polled-per-byte access like for serial the overhead robs it. Better with a GC or SGC, but still, not the 1.5mbaud+ we're looking for.

This needs a custom external solution.

[Derek_Stewart]

Hi Dave,

There was a Fast Serial Port inteface designed by Terry Harman, software was written by Phil Borman.

The design files are on the QL Homepage.

I suppose the interface could be built. Would you be interested in a completed interface.

I looked at that but didn't find the ROM image - thank you for pointing me to it. I tried months ago and wasn't able to extract a usable image from the PCL file, but I could tell enough to see it looked like it was based around the 6402. There aren't any other ICs that offer an upgrade path from the 6402, which was the last of the 80s-early 90s style of UARTs like the 6850 I'm trying to get away from. I'm trying to provide 2 or 4 ports (2 ext plus internal use) and looking to get up into the 1.5MB/sec area with decent sized FIFOs so the service requirement by SMSQ/QDOS is low. Don't get me wrong - the 6402 is capable of going quite fast. It just really limits future possibilities.

I guess this means there isn't a 68681-type interface out there at all

Thank you for offering to build one.

Here is the PDF version of the Schematic file.

I has looking to do Kicad version of the schematic file, just as a design exercise to get better used to the Kicad software.

There is a Resident extension file, which could be made romable, but not on the the Serial card. SO not much use.

[Dave]

Ooooh, this is SO much easier to read! Thank you! When I tried converting it, it lost 3/4 of the pixels - most of the lines and characters turned to mush.

Interesting to see how they put a small external FIFO (512Kx9) on either side of the UART. The only thing I'd change is to put the driver in ROM.

Surprisingly, the UART is quite cheap, but the FIFOs are cripplingly expensive today.