ROMboot

At power-up, the tape controller positions the streaming tape to load point where the volume ID can correctly be read and used.

If, however, the MVME177 loses power but the controller does not, and the tape happens to be at load point, the sequences of commands required (attach and rewind) cannot be given to the controller and autoboot will not be successful.

ROMboot

The ROMboot function is configured/enabled by the Environment (ENV) command (refer to Commands Table at the end of this Appendix) and executes:

At power-up

At reset (optionally)

By the RB command, assuming there is valid code in the EPROMs (or optionally elsewhere on the module or VMEbus) to support it.

If ROMboot code is installed, a user-written routine is given control (if the routine meets the format requirements). One use of ROMboot might be resetting SYSFAIL* on an unintelligent controller module. The NORB command disables the function.

For a user's ROMboot module to gain control through the

ROMboot linkage, four requirements must be met:

Power must have just been applied (but the ENV command can change this to also respond to any reset)

Your routine must be located within the MVME177 ROM memory map (but the ENV command can change this to any other portion of the onboard memory, or even offboard VMEbus memory)

B

B-5

Page 85
Image 85
Motorola MVME177 manual ROMboot