Rainbow Electronics AT90S8515 - Manual (Page 18)

18
AT90S8515
0841G–09/01
Figure 20. The Parallel Instruction Fetches and Instruction Executions
Figure 21 shows the internal timing concept for the register file. In a single clock cycle
an ALU operation using two register operands is executed and the result is stored back
to the destination register.
Figure 21. Single Cycle ALU Operation
The internal data SRAM access is performed in two System Clock cycles as described
in Figure 22.
Figure 22. On-chip Data SRAM Access Cycles
See “Interface to External SRAM” on page 60 for a description of the access to the
external SRAM.
System Clock Ø
1st Instruction Fetch
1st Instruction Execute
2nd Instruction Fetch
2nd Instruction Execute
3rd Instruction Fetch
3rd Instruction Execute
4th Instruction Fetch
T1 T2 T3 T4
System Clock Ø
Total Execution Time
Register Operands Fetch
ALU Operation Execute
Result Write Back
T1 T2 T3 T4
System Clock Ø
WR
RD
Data
Data
Address Address
T1 T2 T3 T4
Prev. Address
Read
Wr
ite