C167CS-4RM datasheet(61/517 Pages) INFINEON

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C167CS

Derivatives

The Central Processing Unit (CPU)

User’s Manual

4-11

V2.0, 2000-07

4.4

Instruction State Times

Basically, the time to execute an instruction depends on where the instruction is fetched

from, and where possible operands are read from or written to. The fastest processing

mode of the C167CS is to execute a program fetched from the internal code memory. In

that case most of the instructions can be processed within just one machine cycle, which

is also the general minimum execution time.

All external memory accesses are performed by the C167CS’s on-chip External Bus

Controller (EBC), which works in parallel with the CPU.

This section summarizes the execution times in a very condensed way. A detailed

description of the execution times for the various instructions and the specific exceptions

can be found in the “C166 Family Instruction Set Manual”.

Table 4-1 shows the minimum execution times required to process a C167CS instruction

fetched from the internal code memory, the internal RAM or from external memory.

These execution times apply to most of the C167CS instructions - except some of the

branches, the multiplication, the division and a special move instruction. In case of

internal ROM program execution there is no execution time dependency on the

instruction length except for some special branch situations. The numbers in the table

are in units of CPU clock cycles and assume no waitstates.

Execution from the internal RAM provides flexibility in terms of loadable and modifyable

code on the account of execution time.

Execution from external memory strongly depends on the selected bus mode and the

programming of the bus cycles (waitstates).

Table 4-1

Minimum Execution Times

Instruction Fetch

Word Operand Access

Memory Area

Word

Instruction

Doubleword

Instruction

Read from

Write to

Internal code memory

–

Internal RAM

0/1

16-bit Demux Bus

16-bit Mux Bus

8-bit Demux Bus

8-bit Mux Bus

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