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
Destination
h
= 00h
0000h
Word1
h
Word1
l
8001h
Destination
l
= 00h
•
Word2
h
Word2
l
8002h
Length N
h
•
•
.
•
8003h
Length N
l
•
•
•
8004h
Word1
h
nnnEh
•
•
8005h
Word1
l
nnnFh
Wordn
h
Wordn
l
8006h
Word2
h
8007h
Word2
l
•
•
•
•
•
•
nnnEh
Wordn
h
nnnFh
Wordn
l
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.