Advantech RS-485 user manual Bit 7 cannot be enabled in the ADAM-5018 since

Command Set		5017/5018 Analog Input
$aaSi5mm			$aaSi5mm
Name	Enable/Disable Channels for multiplexing
Description	Enables/Disables multiplexing for separate channels of
	the specified input module
Syntax	$aaSi5mm(cr)
	$ is a delimiter character.
	aa (range 00-FF) represents the 2-character hexadecimal
	address of the ADAM-5000 system.
	Si identifies the I/O slot of the system.
	5 identifies the enable/disable channels command.
	mm are two hexadecimal values. Each value is interpret-
	ed as 4 bits. The first 4-bit value represents the status of
	channels 4-7, the second 4 bit value represents the
	status of channels 0-3. A value of		0 means the channel
	is disabled, while a value of 1 means the channel is
	enabled. (See the Read Channel Status Command
	$aaSi6)
Note:	Bit 7 cannot be enabled in the ADAM-5018 since the
	module is physically limited to 7 channels.
	(cr) is the terminating character, carriage return (0Dh)
Response	!aa(cr) if the command is valid.
	?aa(cr) if an invalid operation was entered.

There is no response if the module detects a syntax error or communication error or if the specified address does not exist.

! delimiter character indicating a valid command was received.

? delimiter character indicating the command was invalid.

6-42 ADAM-5000