AR# 3497: F1.x State Machine Editor: Syntax Error 1031: Undefined identifier name 'SREG0'
AR# 3497
F1.x State Machine Editor: Syntax Error 1031: Undefined identifier name 'SREG0'
Description
Keywords: user-defined encoding, XABEL, state machine
Urgency: Standard
General Description:
Specifying the encoding scheme as user-defined in Foundation 1.x State Editor and then trying to synthesize the state machine gives an error message resembling this:
Syntax Error 1031: Undefined identifier name 'SREG0'
as well as several other error messages.
The cause of this error is that state register declarations are left out in the ABEL code generated for the user-defined encoding scheme.
One can observe this behavior by comparing the ABEL code generated for a binary encoded state machine to that generated for a user-defined encoded state machine. In the declaration section of an 8-state state machine one should observe the following lines:
As can be seen S1..S7 are assigned states in alpha-numerical order. If one were to use user-defined encoding for the same state assignments the code generated would look like:
"******** USER DEFINED ENCODED state machine: Sreg0 ****** "******** "******** !!!! USER have to declare: STATE REGISTER & ALL STATES CODES !!!!
Very obvious from the above code is that the state register definitions are missing. The error results from the missing state register definitions.
Solution
1
As shown in the general description just cut & paste the state register declarations from the code generated for a binary encoded state machine into the code for the user-defined code. From state machine editor: Synthesis -> HDL Code Generation
When modifying the code in HDL editor make sure that the Edit -> Read Only option is unchecked so that the necessary modifications can be made. One can also modify the user defined encoded states in the generated code file using HDL editor. Save this file and synthesize directly from HDL editor (Synthesis -> Synthesize). Now a macro for the state machine can also be created directly from the HDL editor.
Note: If one goes back to state editor and re-generates HDL code for the state machine the previous version will be overwritten. Hence one has to make sure to make the necessary modifications again whenever any changes are made to the state machine. This may turn out to be a hassle over a longer period of time. A simpler alternative is resolution 2.
2
In state machine editor label the states in alphabetical order the way one would have labeled the user-defined numerical order. For example for a 4-state state machine:
S1 = 3; S2 = 2; S3 = 0; S4 = 1;
This would classify under the user-defined encoding scheme. One could implement this same sheme using binary encoding just by renaming the state names in state editor as follows:
S3 is A, S4 is B, S2 is C and S1 is D OR S3 is aardvark, S4 is acrobat, S2 is architect, S1 is burglar and so on...
Since the state editor assigns state-number assignments in aplhabetical order the above renaming would pass as binary encoding and will also implement the desired user-defined encoding.