Difference between revisions of "III/VC SCM"
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= Main Section = | = Main Section = | ||
Made up of many opcodes one after the other. Opcodes are of the format: | Made up of many opcodes one after the other. Opcodes are of the format: | ||
| − | + | <source lang="c">TOpcode { | |
| − | + | Opcode[2]: Word; //Opocode number in word format | |
| − | + | Parameters: Array Of TParameter; | |
| − | + | }</source> | |
The number of parameters is specific for each opcode. The [http://vc-db.webtools4you.net/ opcode database] has all of the opcodes in VC, with their parameter numbers, and for most, a description of what they do. | The number of parameters is specific for each opcode. The [http://vc-db.webtools4you.net/ opcode database] has all of the opcodes in VC, with their parameter numbers, and for most, a description of what they do. | ||
Parameters are of the format: | Parameters are of the format: | ||
| − | + | <source lang="c">TParameter { | |
| − | + | ParameterType[1]: Byte; //Says which type of parameter will follow | |
| − | + | ActualParameter: varies; //The actual parameter | |
| − | + | }</source> | |
The parameter types are as follows (but there are more in SA): | The parameter types are as follows (but there are more in SA): | ||
01: 32-bit int (DWord) | 01: 32-bit int (DWord) | ||
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Global vars reference a position in the file much like a label. There is a space at the top of the scm file filled with 00's which is space reserved for global vars. This is divided into blocks of 4 bytes, each var taking up one of these blocks. In compiled form, the global vars each point to somewhere in that block (or should do as otherwise writing to it will modify the actual code). | Global vars reference a position in the file much like a label. There is a space at the top of the scm file filled with 00's which is space reserved for global vars. This is divided into blocks of 4 bytes, each var taking up one of these blocks. In compiled form, the global vars each point to somewhere in that block (or should do as otherwise writing to it will modify the actual code). | ||
== Example == | == Example == | ||
| − | + | This code: | |
| − | + | <source lang="scm">0001: wait 8 ms | |
| − | + | 0002: jump $var1 | |
| − | + | 0050: gosub 1@ | |
| − | + | 0051: return</source> | |
| − | + | compiles as: | |
01 00 04 08 //wait opcode (First 2 bytes = opcode, next byte = 04 the parameter type for 8-bit int, and 08 is the actual value) | 01 00 04 08 //wait opcode (First 2 bytes = opcode, next byte = 04 the parameter type for 8-bit int, and 08 is the actual value) | ||
02 00 02 18 00 // jump opcode. The 18 00 would mean that the global var is stored at address 0x0018 | 02 00 02 18 00 // jump opcode. The 18 00 would mean that the global var is stored at address 0x0018 | ||
Revision as of 18:13, 2 February 2009
Overall Format
(02 00 01)h + 32 bit int Jump to second segment byte Padding (Global vars) Space for variable saving (02 00 01)h + 32 bit int Jump to third segment byte Segment id 32 bit int Number of models (model names) 24 byte model names * number of models(model 0 not used) (02 00 01)h + 32 bit int Jump to fourth segment byte Segment id 8 bytes Padding/mysterious, unused data 32 bit int Number of missions (mission addresses) 32 bit addresses * number of missions (MAIN code) MAIN section, equal to size defined earlier (mission code) The mission data, missions stored at offsets defined earlier
Main Section
Made up of many opcodes one after the other. Opcodes are of the format:
TOpcode {
Opcode[2]: Word; //Opocode number in word format
Parameters: Array Of TParameter;
}The number of parameters is specific for each opcode. The opcode database has all of the opcodes in VC, with their parameter numbers, and for most, a description of what they do. Parameters are of the format:
TParameter {
ParameterType[1]: Byte; //Says which type of parameter will follow
ActualParameter: varies; //The actual parameter
}The parameter types are as follows (but there are more in SA):
01: 32-bit int (DWord) 02: global var (Word) 03: local var (Word) 04: 8-bit int (Byte) 05: 16-bit int (Word) 06: 4-byte float (Single)
Labels use the type 01 (although if they address is small enough using data types 04 and 05 will also work). Global and local vars can also be used for labels. Global vars reference a position in the file much like a label. There is a space at the top of the scm file filled with 00's which is space reserved for global vars. This is divided into blocks of 4 bytes, each var taking up one of these blocks. In compiled form, the global vars each point to somewhere in that block (or should do as otherwise writing to it will modify the actual code).
Example
This code:
0001: wait 8 ms
0002: jump $var1
0050: gosub 1@
0051: returncompiles as:
01 00 04 08 //wait opcode (First 2 bytes = opcode, next byte = 04 the parameter type for 8-bit int, and 08 is the actual value) 02 00 02 18 00 // jump opcode. The 18 00 would mean that the global var is stored at address 0x0018 50 00 03 01 00 //the gosub opcode 51 00 //the return opcode (it has no parameters)
