HP-IL checksums or not

[Christoph Giesselink]

(11-27-2017 07:04 PM)hth Wrote:  

(11-27-2017 05:58 PM)Christoph Giesselink Wrote:  Last rhetorical question, how do you verify data transfers on HP-IL when the controller is listener and one device is talker?

HP-IL read transfers are verified by the talker (storage device), it sends a DAB (Data Byte) which is passed around the loop, the controller takes the data and passes it on. When it gets back to the talker it checks that it gets back what it sent out, if it is correct it sends the next frame until the ending ETO (end of transmission OK) frame. If a transmission error is detected (it did not get the same DAB back), it will terminate with an ETE frame (end of transmission - error).

Good we talk about. I wasn't aware about this. I only known the protocol from the virtual device implementation side and these are imcomplete. JFG's original ILPer implementation and all successors like ILPer 2.x, pyILPer, ILVideo, .... don't contain the talker error checking, they always return the ETO and never the ETE frame at end of transmission.

Even more all virtual controllers, like Emu71/Win (also in device configuration) don't verify what they received in most conditions so they don't recognize transfer errors too.

It should not be too difficult to add ETE in the TALKER implementation of the devices, but the HP-IL simulation inside Emu71 wasn't designed for this.