C161 Datasheet, PDF (60/400 Pages) Infineon Technologies AG – 16-Bit Single-Chip Microcontroller

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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 C161PI 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 C161PI’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 detailled
description of the execution times for the various instructions and the specific exceptions
can be found in the “C16x Family Instruction Set Manual”.
The table below shows the minimum execution times required to process a C161PI
instruction fetched from the internal code memory, the internal RAM or from external
memory. These execution times apply to most of the C161PI 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.
Table 4-1 Minimum Execution Times
Instruction Fetch
Word Operand Access
Memory Area
Word
Doubleword Read from
Instruction Instruction
Write to
Internal code memory
2
Internal RAM
6
2
2
---
8
0/1
0
16-bit Demux Bus
2
16-bit Mux Bus
3
4
2
2
6
3
3
8-bit Demux Bus
8-bit Mux Bus
4
8
4
4
6
12
6
6
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).
User’s Manual
4-12
1999-08