M8189 bootstrap error LED's D1 and D4 on

[cmao]

> so...the termination is required?

Termination is used to damp the reflection of signals on the end of a bus, otherwise, it bounces back and messes with the emitted signal. As I remember this effect is particularly strong if the travel time of the signal is shorter than it's rising and lowering times.
This means than for one-meter (~yard) length, the edge times should be (roughly) slower than 5 nanoseconds as electricity travels at ~200.000km/sec.
But in TTL signals, edge times are at ~5nanoseconds, so there is a need for resistors.
(sorry for my broken English)

I will make a simple small PCB populated with 180ohms and 390ohm resistors as shown in the pdf file. I plan to place the PCB on the back side of the backplane with the help of the wire wrap pins.

It seems no termination is required for C and D slots ??? Can I add terminators to both AB and CD.

 

[cmao]

I will make a simple small PCB populated with 180ohms and 390ohm resistors as shown in the pdf file. I plan to place the PCB on the back side of the backplane with the help of the wire wrap pins.

It seems no termination is required for C and D slots ??? Can I add terminators to both AB and CD.

I think it doesn't make sense to add terminators to both AB and CD. I would think the terminator should be added to CD instead of AB.

 

[cmao]

I asked AI. Below is the answer from OpenAI...

"
## Bing
Yes, QBus requires bus terminator. The backplane in the BA23 chassis (H9278A) has four onboard socketed resistor packs for termination, so a separate terminator board is not required.
"
I have made a simple terminator. As soon as I have it, I will test it on my backplane.

 

[MattisLind]

A short backplane doesn't require terminators. The CPU board is terminating one end and for single backplane system it is enough. I have a H9270 4x4 backplane with M8189, some memory and a Viking SCSI which works just fine without any extra terminators at the far end of the backplane. H9278 has sockets for SIL terminator packs.