95
In addition, four other messages are used in sample dump communication:
Sample Dump Request
Cancel Dump
Not Acknowledge
Acknowledge
The data sequence and "handshaking" are as follows.
The master either receives a dump request which includes the sample number,
or a dump of the current sample is initiated from the front panel. In either case,
the master transmits the header message, and waits for no less than two
seconds for the slave to decide if it will accept this dump.
The slave reads the header, and checks the sample characteristics (rate,
length, and so on) to see if the sample can be accepted. If the slave will
recognize the dump, it sends an Acknowledge. If the slave refuses to accept
the dump (for example, due to excessive size or unacceptable rate), it sends a
Cancel Dump abort command and returns to normal operation.
If within two seconds a Cancel Dump message is received, the master aborts
the dump mode by transmitting an F7 (End of Exclusive), and returns to normal
operation. If the master receives the Acknowledge (closed-loop), or if after two
seconds it receives nothing (open-loop), it proceeds with the data dump by
sending the rst data packet, and waits for 20 milliseconds while checking its
MIDI input.
The slave receives the packet, checks the packet number to see whether it is a
new packet or just a repeat of a previous packet, and compares the checksum
at the end. If the checksum matches, the slave transmits an Acknowledge
(which means in this case, "The last packet was received okay. Send the next
one."). If the checksum does not match, this indicates an error in the packet,
so the slave transmits a Not Acknowledge (which means "The last packet had
an error. Send it again.") and prepares to receive data. If the slave sends a Not
Acknowledge, then sees that the master has incremented the packet number
anyway (on the next transmission), it concludes that the master did not receive
the Not Acknowledge, so there is an open loop. It may either abort or ignore
the error. The Prophet-VS ignores the error.
As soon as the master receives an Acknowledge, it immediately increments
the packet number and transmits the next packet. If it received a Not
Acknowledge, it keeps the packet number the same and re-transmits the
packet. If it receives a Cancel Dump, it will of course abort the dump. If
nothing comes in within 20 milliseconds, it proceeds as if an Acknowledge
were received.
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