PROG File Format
The :PROG file format
Header 1 : 1 256-word (512-byte) header block
N : N 256-word blocks, up to a maximum of 255 blocks
Header 2 : 1 256-word (512-byte) header block, starting at
file byte offset 0x20000 (or 131072)
M : M 256-word blocks, starting at file byte offset 0x20200,
up to a maximum of either 255 or 256 blocks (TBD).
The 'Header 2' and 'M' sections are optional (used for 2-bank programs only).
Header block layout
Start address : 16-bit word, big endian Restart address : 16-bit word, big endian First address Bank 1 : 16-bit word, big endian Last address Bank 1 : 16-bit word, big endian First address Bank 2 : 16-bit word, big endian Last address Bank 2 : 16-bit word, big endian
First address is where in the memory map of the (bank1/bank2) segment the image data (N or M) should be loaded, and the number of words to load is:
(Last address - First address) + 1
For 1-bank programs First address Bank 2, Last address Bank 2 are always 0xffff 0x0000, indicating no data. In this case there will be no Header 2/M sections in the :PROG file.
2-bank programs will often have a hole (unallocated disk pages) in the :PROG file, after end of N and start of Header 2, because Header 2 always starts at byte offset 0x20000. Also note that because of this, and the header block, a :PROG file cannot have a bank 1 larger than 256 words less than the maximum ND-100 virtual memory size (64Kw). Bank 2 can be a full 64Kw.
(Because of the possibility for a hole in 2-bank :PROG files, care must be taken when copying such files over from a Norsk Data system to somewhere else. The FTP program, for example, will mishandle the file.)
Example: 2-Bank program
(this is actually a version of the BRF-LINKER)
Start address : 026111 Restart address : 026111 First address Bank 1 : 0 Last address Bank 1 : 071560 First address Bank 2 : 0 Last address Bank 2 : 024263
This is a 2-bank program. To load the file, prepare two 64-kiloword areas (the first shall be accessed through the normal page table, the second through the alternative page table. The application will call Mon ALTON early on, to enable the alternative page table.) Copy ((071560 - 0) + 1) * 2 bytes from byte offset 512 in the :PROG file into area 1, at offset 0 and onwards. Copy ((024263 - 0) + 1) * 2 bytes from byte offset 131584 (which is 131072+512) in the :PROG file into area 2, at offset 0 and onwards. The application shall start execution from address 026111.
Example: 1-Bank program
Start address : 0177777 Restart address : 0177775 First address Bank 1 : 0145000 Last address Bank 1 : 0177777 First address Bank 2 : 0177777 Last address Bank 2 : 0
This is a 1-bank program. Prepare a 64-kiloword area. Copy ((01777777 - 0145000) + 1) * 2 bytes from byte offset 512 in the :PROG file into the area, at offset 0145000 and onwards. Nothing is loaded into low memory (below address 0145000) in this case. The application shall start execution from address 0177777 (and that will have to be a JMP instruction with negative displacement, as it is the last word in the address range).