Advantage of using Specman Elite stimulus variation feature

The Specman elite e-language stimulus Variation concept mainly helps in,

· Reusability
· Maintainability
· Extendibility

An Approach to Creating SUBTYPES using e-language:
Consider a Network Packet example having address, length, data as its fields and using the defined fileds need to calculate parity . The defined Network Packet may be either GOOD or BAD.
Whenever the packet is of type GOOD assign the parity calculated to parity field and if the packet is of type BAD then do not assign the parity to the parity field.
In order to achieve the required condition, we need to create a subtype using when inheritance.

Following are the steps to be taken while creating subtypes.
· Define a new enumerated type (i.e. Good and Bad)
· Define a field on enumerated type in the struct to represent various subtypes.
· Write a when block and add struct members in the when block that correspond to properties of the specific subtypes.

filename : packet.e
<’
---- Declaration of enumerated types
type packet_kind_t: [Good, Bad];
struct packet_s {
pkt_Kind: packet_kind_t;
Address : uint (bits: 2);
Length : uint (bits: 6);
Data : list of byte;
Keep data. size () = = length;
Parity : byte;
---- User Method for calculating parity Value
Parity_calc () : byte is {
----- User Actions Needs to be entered for calculating parity;
};
--- Subtype creation
When Good ‘pkt_kind packet_s {
Keep parity = = parity_calc ();
};
When Bad ‘pkt_kind packet_s {
Keep parity! = Parity_calc ();
};
};
‘> ---- End of struct

filename : packet_top.e

<'
import packet.e;
extend sys {
packet : packet_s ;
};
'>

filename : packet_test.e
<'
import packet_top.e;
// For Writing Test cases using constraint use the extend feature supported by e-language
extend packet_s {
// Apply the Constraints Required
keep soft pkt_kind == GOOD;
keep soft length == 10;
keep soft Address in [0x1000..0x2000];
};
'>