Denon AVR-2311CI Service Manual page 25

(2) When connection is good, then you can see the "Communication check OK." message.
(3) If connection is not good, then you can see the "Communication error!" message.
Please confirm the following
(a) Check the connection of the AV receiver/amplifier and PC. (refer to "2.Connection to AV ..." )
(b) Check the operation mode of the AV receiver/amplifier. (refer to "3.Turn on the AV ...")
(c) Check the selection of the RS-232C port number of PC.
6. Download the firmware
(1) Click the "Select" button.
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