Question: A 68020-based single-board microprocessor system is to be used to keep track of items in a shop. The shop sells up to N items. Each item is characterized by its 28-byte ASCII-encoded name followed by a longword pointer. This pointer points to the actual record that describes the item. A record consists of a 256-byte text field that describes the item, followed by four consecutive 4-byte fields. These fields define the item's cost price, selling price, number bought, and number sold. Suppose you need to access field x of item. Before accessing the field, you may assume that the 68000 registers have been set up as follows

AO points at the first item in the list of N items

• DO contains item number y and is in the range 0 to N 1

• D1 contains the field number x and is in the range 0 to 3

a. Draw a map to illustrate the above data structure.

b. Show how you would use the 68000 microprocessor to access field x of item y from the data structure.

c. Show how you would use the memory indirect addressing mechanism of the 68020 to access the same field in the data structure.