Binary Relocatable Format
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BRF code is a stream of eight-bit bytes and can be stored on any data medium (tape, file etc). The information can be divided into the following three basic types:
- Control information: A single byte, the control number. This is interpreted as a linker command.
- Programmed information: Two bytes containing a 16-bit word, called a P-group
- Symbolic information in either four bytes for MAC or NPL, or six bytes for BRF produced by compilers (e.g. FORTRAN). This is called an S-group and contains a symbol of one to seven packed six-bit characters.
BRF code are sequences of BRF groups, where each BRF group is a a combination of the three basic types. A BRF group can take one of the following four forms:
<control number byte> <control number byte><P-group><P-group> <control number byte><S-group> <control number byte><S-group><P-group>
The possible values and meaning of the control numbers are described in the following table. 'Words' are 16-bits words in big endian format.
| Control Number | Mnemonic | Argument size in words | Interpretation |
|---|---|---|---|
| 08 | FEED | 0 | Ignored |
| 18 | LF | 1 | W1 -> ((CLC)), (CLC)+1 -> (CLC) |
| 28 | LR | 1 | W1+(PB) -> ((CLC)),(CLC)+1 -> (CLC) |
| 38 | LC | 1 | W1+(CDB) -> ((CLC)),(CLC)+1 -> (CLC) |
| 48 | AFF | 2 | W1+(W2)->(W2) |
| 58 | ARF | 2 | W1+(PB)+(W2) -> (W2) |
| 68 | AFR | 2 | W1+(W2+(PB)) -> (W2+(PB)) |
| 78 | ARR | 2 | W1+(PB)+(W2+(PB)) -> (W2+(PB)) |
| 108 | SFL | 1 | W1 -> (CLC) |
| 118 | AFL | 1 | W1+(CLC) -> (CLC), fill zeroes |
| 128 | SRL | 1 | W1+(PB) -> (CLC) |
| 138 | - | Not used | |
| 148 | MAIN | 2 (3) | Symbol in S-group will become the main entry. Size of S-group depends on LONG control number. |
| 158 | LIBR | 2 (3) | Symbol in S-group will be conditionally loaded |
| 168 | ENTR | 2 (3) | Symbol in the S-group is assigned value of CLC |
| 178 | BEG | 0 | (CLC) -> (PB) First control byte of a unit. Linker-managed counters reset. |
| 208 | REF | 2 (3) | Symbol in S-group is referenced in CLC |
| 218 | END | 1 | W1 contains the BRF checksum |
| 228 | INHB | 1 | Warns that compilation errors have occured |
| 238 | EOF | 0 | End of loading |
| 248 | LNF | 1+W1 | W2,W3....,Wn -> (CLC),....,(CLC+W1-1) |
| 258 | RT | 1 | W1 contains real time priority |
| 268 | ASF | 3 (4) | <symbol>,<number> Defines common length. Value of symbol in loader table = common start address. |
| 278 | ADS | 2 (3) | <symbol> + (CLC-1) -> (CLC-1) Adds common address |
| 308 | MSG | 1+W1 | W1 contains length of message in words: W1 is followed by W1*2 ASCII character bytes |
| 318 | - | Not used | |
| 328 | LONG | 0 | Flags a six-byte S-group (see MAIN,LIBR,ENTR,REF,ASF,ADS,INC,DBC,RLC,CXC) |
| 338 | - | Not used | |
| 348 | INL | 2 | W2 -> (W1+(PB)) |
| 358 | DBL | 3 | Wi -> (W1+(BP)+i-2) (i = 2 to 3) |
| 368 | RLL | 4 | Wi -> (W1+(PB)+i-2) (i = 2 to 4) |
| 378 | CLX | 7 | Wi -> (W1+(PB)+i-2) (i = 2 to 7) |
| 408 * | INC | 4 (5) | W5 -> (W4 + ADR) |
| 418 * | DBC | 5 (6) | Wi -> (W4 + ADR + i-5) (i = 5 to 6) |
| 428 * | RLC | 6 (7) | Wi -> (W4 + ADR + i-5) (i = 5 to 7) |
| 438 * | CXC | 9 (10) | Wi -> W4 + ADR + i-5) (i = 5 to 10) |
| 448 | BYL | 2 | W2(bit 0-7) -> (W1+(PB))(bit 0-7) if W2 bit 15=0 |
| W2(bit 0-7) -> (W1+(PB))(bit 8-15) if W2 bit 15=1 | |||
| 458 * | BYC | 5 | W5(bit 0-7) -> (W4+(ADR))(bit 0-7) if W5 bit 15=0 |
| W5(bit 0-7) -> (W4+(ADR))(bit 8-15) if W5 bit 15=1 | |||
| 468 | NWL | 1 | W1 contains line number. (Not in use.) |
| 478 | DBG | 0 | Indicates start/stop of Debug information |
| 508 | PMO | 0 | Indicates start of program bank mode |
| 518 | DMO | 0 | Indicates start of data bank mode |
| 528 | LRP | 1 | Same as LR but PB of program bank |
| 538 | LRD | 1 | Same as LR but PB of data bank |
| 548 | DIC | - | Dictionary table follows. Each element contains name (3 words) and byte pointer (2 words). End of table marked by -1 |
| * The W1, W2, and W3 contains a common block name. At load time the symbol must be defined. Its value is referred to as ADR. | |||
The BRF Linker can also be used to inspect BRF code. The example below shows how to look at a single library function, "5STOP" (an internal Fortran function) from the Fortran-100 2-bank library file FORTRAN-2BANK:BRF. The BRF Linker command LIST-BRF-CODE is used to show the library entry.
- BRF Linker - 210721C01
Brl: list-brf-code
Input file :fortran-2bank
First unit :5stop
Last unit :5stop
Output file:
1 17 BEG *** new BRF - unit ***
1 32 LONG
1 51 DMO
1 15 LIBR 5STOP
1 50 PMO
1 16 ENTR 5STOP
1 24 LNF 3
1 146147 COPY SL DX
2 135024 JPL I * 24
3 0 STZ *
4 20 REF 5STACK
5 24 LNF 21
5 600 STZ ,B - 200
6 1 STZ * 1
7 0 STZ *
10 146157 COPY SA DX
11 46000 LDA ,X 0
12 4606 STA ,B - 172
13 46001 LDA ,X 1
14 4607 STA ,B - 171
15 44606 LDA ,B - 172
16 4406 STA ,B 6
17 44607 LDA ,B - 171
20 4407 STA ,B 7
21 44602 LDA ,B - 176
22 172406 AAA 6
23 171002 SAT 2
24 135003 JPL I * 3
25 135003 JPL I * 3
26 20 REF 5INIT
27 20 REF 5MSTOP
30 20 REF 5LEAV
31 51 DMO
1 50 PMO
31 6 AFR 2,3
31 6 AFR 210,20
31 6 AFR 210,16
31 51 DMO
1 50 PMO
31 21 END checksum : 27512
Brl:
References
- Norsk Data Document ND–60.196.01 BRF-LINKER USER MANUAL Chapter 6