SH7751 Datasheet, PDF (320/1224 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer

8. Pipelining
Table 8.2 Parallel-Executability
2nd Instruction
MT EX BR LS FE CO
1st
MT
Instruction _EX
O
O
O
O
O
X
O
X
O
O
O
X
BR
O
O
X
O
O
X
LS
O
O
O
X
O
X
FE
O
O
O
O
X
X
CO
X
X
X
X
X
X
Legend:
O: Can be executed in parallel
X: Cannot be executed in parallel
8.3 Execution Cycles and Pipeline Stalling
There are three basic clocks in this processor: the I-clock, B-clock, and P-clock. Each hardware
unit operates on one of these clocks, as follows:
• I-clock: CPU, FPU, MMU, caches
• B-clock: External bus controller
• P-clock: Peripheral units
The frequency ratios of the three clocks are determined with the frequency control register
(FRQCR). In this section, machine cycles are based on the I-clock unless otherwise specified. For
details of FRQCR, see section 10, Clock Oscillation Circuits.
Instruction execution cycles are summarized in table 8.3. Penalty cycles due to a pipeline stall or
freeze are not considered in this table.
• Issue rate: Interval between the issue of an instruction and that of the next instruction
• Latency: Interval between the issue of an instruction and the generation of its result
(completion)
• Instruction execution pattern (see figure 8.2)
• Lock stage: Locked pipeline stages(see table 8.3)
• Lock start: Interval between the issue of an instruction and the start of locking (see table 8.3)
• Lock cycle: Lock time (see table 8.3)
Rev.4.00 Oct. 10, 2008 Page 222 of 1122
REJ09B0370-0400