Boot Code
At startup, TOF
\ Boot sequence:
\ Evaluate primary boot code (in target board's EEPROM)
\ Initialize the expansion interface
\ Select node 0
\ BEGIN Attempt to evaluate boot code from the node.
\ If valid boot code, append the node number to the active list.
\ Select the next node
\ UNTIL four consecutive invalid boot devices are found.
\ Evaluate secondary boot code (in target board's EEPROM)
\ External devices contain the following boilerplate in their
boot EEPROMs:
\ byte contents (big endian)
\ 000 0xC0DE indicates that this EEPROM contains code
\ 002 Vendor key (00=generic)
\ 003 0x07C9
\ 005 16-bit checksum
\ 007 24-bit length
\ 00A code...
\ 7FF last usable byte in 25C160 EEPROM