Embedded Systems: An Integrated Approach by Pearson

352 EMBEDDED SYSTEMS

If the address of a 32-bit number is given as 0x1200, the accessed addresses are

0x1200, 0x1201, 0x1202 and 0x1203.  e 4 bytes in these addresses are considered to be

in the same row, that is, aligned. In this case, one byte each from each bank is accessed

and only one memory cycle is needed to access an aligned word.

For unaligned data, one more cycle is necessary.  ink of the address 0x1201.  e

locations to be accessed will be 0x1201, 0x1202, 0x1203 and 0x1204. Note that the fi rst

three bytes will be in the same row, while the last will be in a diff erent row (bank), and

so one more cycle of access will be required.

We summarize the conditions for ‘aligned data’ as follows:

• For word (32-bit) data, the specifi ed address ...