How a HP-IL peripheral signals "no more data"
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02-03-2018, 10:06 AM
(This post was last modified: 02-03-2018 10:30 AM by J-F Garnier.)
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RE: How a HP-IL peripheral signals "no more data"
This is definitively not a question of "newbie" !
To keep it simple: generally the right way for a device to signal no (or no more) data available is to reply with EOT (End of Transmission). Then, it's up to the controller to decide what to do: if the controller is happy with this reply, the transaction is over (the 41C acts in this way), or if the controller explicitly needs a end of data terminator such as CR/LF, the controller may retry with a new SDA (Send Data). The HP71B can act in both ways: by default it will do SDA reties until a termination condition is met (CR/LF, END byte or number of bytes), but can also end the transaction like the 41C when an EOT is received, if the flag -23 is set. Both ways have con and pro: in the one case, the transfer never hangs but may be incomplete and require a new explicit transfer retry; in the other case, the transfer will automatically continue until completion but may hang if the device never send the requested data. J-F |
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Messages In This Thread |
How a HP-IL peripheral signals "no more data" - cgh - 02-02-2018, 07:55 PM
RE: How a HP-IL peripheral signals "no more data" - cgh - 02-03-2018, 07:38 AM
RE: How a HP-IL peripheral signals "no more data" - cgh - 02-03-2018, 09:52 AM
RE: How a HP-IL peripheral signals "no more data" - J-F Garnier - 02-03-2018 10:06 AM
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