Issuer Scripts on Verifone Vx PIN pads

Question

Does anyone know how the issuer script processing flow is supposed to work on VeriFone PIN pads? As I understand it, the card processor sends back the script(s) in a 9f18 tag. The scripts marked with 71 tag are to be processed prior to the second Generate AC and the one marked with 72 tag are to be processed after. My question is, what are the sequence of commands, C34, C25 in each case? I suppose you can have one or more 71s and 72s at the same time. The VeriFone API specification says this:

Re C25: "This command contains the scripts that are received from the host. The script results are returned in the C34 response."

Also, "All scripts need to be initialized by sending a C34 to the PINpad"

So, it's not clear if you send all the C25s, one for each script, and then a C34 or perhaps the 71s before and then the 72s after the C34.

Answer 1

Send multiple C25's as needed, C25 only supports one script at a time. Do not try to distinguish the 71 and 72 scripts, just send them. After all the scripts, send the C34.

From the Integrators Guide FAQ section:

Q: When receiving a 72 script when do we send the C34 to the pinpad?
A: C34 is always sent after the C25. The pinpad will process based on the script before or after the second generate AC.