projects / pdp11-bin2pdp / blob
© 2017 Aaron Taylor
This is a loader for the PDP-11. It is designed to work in conjunction with the
server.c program, also found in this directory.
Notes:
Configure the loader by setting the registers to different values.
Program is position independent. Addresses are only examples.
All addresses and values are octal.
| Address | Value | Instruction | Description |
|---|---|---|---|
| R0 | 1000 | Starting memory address to store transferred data | |
| R1 | xxxx | Number of bytes to transfer (displayed by server.c) | |
| R2 | 176540 | Address of RCSR register for SLU | |
| R3 | 1000 | Address for program execution after transfer is complete | |
| 70000 | 105712 | TSTB (R2) | Set N=1 in PSW when SLU contains received byte |
| 70002 | 100376 | BPL -> 70000 | Loop until SLU has another byte ready to read |
| 70004 | 116220 | MOVB X(R2) (R0)+ | Copy byte from SLU to memory and increment location |
| 70006 | 2 | X=2 | RCSR + 2 = RBUF |
| 70010 | 005301 | DEC R1 | Decrement number of bytes remaining to receive |
| 70012 | 005701 | TST R1 | Set Z=1 in PSW after receiving last byte |
| 70014 | 001371 | BNE -> 70000 | Loop until all bytes are transferred |
| 70016 | 010307 | MOV R3 R7 | Set new PC and begin execution of new instructions |
If you suspect data transfer problems, the following program will generate a checksum which should match that displayed by server.c during the transfer. Remember to halt after loading the image so it remains unmodified.
| Address | Value | Instruction | Description |
|---|---|---|---|
| R0 | 1000 | Starting memory address | |
| R4 | xxxx | Number of words (not bytes!) to check | |
| R5 | 0 | Checksum will be here after program terminates | |
| 71000 | 062005 | ADD (R0)+ R5 | Add word to checksum |
| 71002 | 005304 | DEC R4 | Decrement number of words to check |
| 71004 | 005704 | TST R4 | Set Z=1 in PSW after checking last word |
| 71006 | 001374 | BNE -> 71000 | Loop until all words are checked |
| 71010 | 000000 | HALT | Halt so user can examine checksum in R5 |