Updated client.txt -> client.md in README.md.

[pdp11-bin2pdp] / README.md

# Overview #

The programs contained in this directoy allow bootstrapping of a completely 
blank PDP-11 from an external host. It is not required that the PDP-11 have any 
pre-existing code in the form of drives or ROMs.

# Status #

The client has been tested with a PDP-11/23+ (KDF11-B on SLU2) and a PDP-11/73
(KDJ11-B with DLV11-J). It should work with most PDP-11 CPUs and SLUs which are
compatible with the DLV11-J register layout.

The server has been tested with a PC running FreeBSD.

# Instructions #

These instructions assume your PDP-11 has a serial connection to a UNIX host,
the `bootstrap_server.c` program has been compiled on the UNIX host, and the
UNIX host has a binary image ready for transfer to the PDP-11.

Begin by loading the program contained in `client.md` into the PDP-11 via the
frontpanel switches or ODT. Set the PDP-11's CPU registers as follows.

  - **R0:** The starting memory address at which the binary image should be stored.

  - **R1:** The number of bytes in the binary image. This information will be displayed
    by `server.c` immediately prior to transfer.

  - **R2:** The base (`RCSR`) register address of the SLU connected to the UNIX host.

  - **R3:** The address to which control should be transferred after the binary image 
    is transferred to the PDP-11.

Begin execution on the PDP-11. If the bootstrap program was loaded at the 
memory addresses listed in `client.md`, begin execution at address `70000`.

Initiate the transfer from the UNIX host with the command

    pdp11-serial-loader -i <binary> -o <port>

where `<port>` is the path to the device file for the serial port connected to
the PDP-11 and `<binary>` is the path to the binary image file. For example, if
using the first serial port under FreeBSD and a binary image named `pdp11.bin`,
execute this command.

    pdp11-serial-loader -i pdp11.bin -o /dev/cuau0

In FreeBSD, add your user to the `dialer` group for permission to access the
serial port.

    pw groupmod dialer -m ataylor
    exec su -l ataylor

Once the binary image has transferred to the PDP-11, it will begin execution at 
the address contained in `R3` which should be your code.

# Binary Image Format #

Since the bootstrap program must be manually toggled into the PDP-11, brevity 
is paramount. Thus, the binary image matches the little-endian byte ordering of 
the PDP-11 word.

Consider the following example program.

    CLR R0
    MOV R0 R1

This would correspond to a binary image with consecutive bytes of:

| Byte | Value    |
| ---- | -------- |
|    0 | 00000000 |
|    1 | 00001010 |
|    2 | 00000001 |
|    3 | 00010000 |

If loaded into memory starting at location `2000`, the PDP-11's memory would
look like this:

| Address | Value            |
| ------- | ---------------- |
|    2000 | 0000101000000000 |
|    2002 | 0001000000000001 |