Boot Loader
4-19
Memory and I/O Spaces
Figure 4–10. Program Code Transferred From 8-Bit EPROM to 16-Bit RAM
8-Bit EPROM 16-Bit RAM
Address 7 0 Address 15 8 7 0
8000h Destinationh = 00h 0000h Word1hWord1l
8001h Destinationl = 00h Word2hWord2l
8002h Length Nh••.
8003h Length Nl•• •
8004h Word1hnnnEh • •
8005h Word1lnnnFh WordnhWordnl
8006h Word2h
8007h Word2l
••
••
••
nnnEh Wordnh
nnnFh Wordnl

The ’C2xx fetches its interrupt vectors from program-memory locations

0000h–003Fh (the reset vector is fetched from 0000h). Make sure that the in-

terrupt vectors are stored at the top of the EPROM, so that they will be trans-

ferred to addresses 0000h–003Fh in the RAM (see Figure 4–11). Each inter-

rupt vector is a branch instruction, which requires four 8-bit words, and there

is space for 32 interrupt vectors. Therefore, the first 128 words to be trans-

ferred from the EPROM should be the interrupt vectors.