Roland REAC R-1000 Reference page 12

Command details
Details of the reply commands
Commands transmitted from the control computer to the R-1000
ack (06H): Active reply
Function Transmitted following successful reception.
Syntax ack (06H) (Command syntax: type 0)
Note This "ack" may be omitted.
ERR: Error
Function Transmitted when a problem occurred in the control computer in response to a command transmitted by the R-1000.
Syntax stxERR:a; (Command syntax: type 2)
a: Error number
0: When the signal from the R-1000 could not be read.
If error number 0 is returned in response to a command sent by the R-1000 in response to a Request command,
the R-1000 will once again transmit the response to that Request command.
In the case of a command that has parameters, the R-1000 will re-transmit the most recently transmitted parameter.
Commands transmitted from the R-1000 to the control computer
ack (06H): Active reply
Function Transmitted following successful reception.
Syntax ack (06H) (Command syntax: type 0)
ERR: Error
Function Transmitted when a problem occurred in the R-1000 in response to a command sent from the control computer.
Syntax stxERR:a; (Command syntax: type 2)
a : Error number
0 : (Syntax error)
Transmitted when the command syntax was incorrect.
2 : (Busy error)
The R-1000 is busy and cannot process the command.
5 : (Out of range error)
The parameter of the received command was out of range.
6 : (Other error)
Some other error has occurred. This will be transmitted if the R-1000 was unable to correctly process the command.
* If one of these commands occurs, the command that was sent to the R-1000 immediately prior to this will be ignored.
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