Binary Relocatable Format

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.

Binary control numbers

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 -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.

References

• Norsk Data Document ND–60.196.01 BRF-LINKER USER MANUAL Chapter 6