Agilent Technologies E4406A VSA Series Programmer's Manual page 401

(-109) Missing parameter
Fewer parameters were received than required for the
header (for example, the *ESE common command
requires one parameter, so receiving *ESE is not
allowed).
(-108) Parameter not allowed
More parameters were received than expected for the
header (for example, the *ESE common command only
accepts one parameter, so receiving *ESE 0,1 is not
allowed).
(-105) GET not allowed
A Group Execute Trigger was received within a
program message (see IEEE 488.2, 7.7). Correct the
GPIB controller program so that the GET does not occur
within a line of GPIB program code.
(-104) Data type error
The parser recognized a data element that is not
allowed (for example, numeric or string data was
expected, but block data was encountered).
(-103) Invalid separator
The parser was expecting a separator and encountered
an illegal character (for example, the semicolon was
omitted after a program message unit).
(-102) Syntax error
An unrecognized command or data type was
encountered (for example, a string was received when
the device does not accept strings).
(-101) Invalid character
A syntactic command contains a character which is
invalid for that type (for example, a header containing
an ampersand, SETUP&).
(-100) Command error
This is a generic syntax error for devices that cannot
detect more specific errors. The code indicates only that
a command error as defined in IEEE 488.2, 11.5.1.1.4
has occurred.
Chapter 6
Error Messages
Error Message Descriptions
401