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SDA 6000
PRELIMINARY DATA SHEET
Version 2.1
C16X Microcontroller
4 - 33
Micronas
Cache Jump Instruction Processing
The CPU incorporates a jump cache to optimize conditional jumps, which are processed
repeatedly within a loop. Whenever a jump on cache is taken, the extra time to fetch the
branch target instruction can be saved, therefore causing the corresponding cache jump
instruction to need only one machine cycle.
This performance is achieved by the following mechanism:
Whenever a cache jump instruction passes through the decode stage of the pipeline for
the first time (and provided that the jump condition is met), the jump target instruction is
fetched as usual, causing a time delay of one machine cycle. In contrast to standard
branch instructions, however, the target instruction of a cache jump instruction (JMPA,
JMPR, JB, JBC, JNB, JNBS) is additionally stored in the cache after having been
fetched.
After repeatedly following each execution of the same cache jump instruction, the jump
target instruction is not fetched from program memory but taken from the cache and
immediately imported into the decoding stage of the pipeline (see
Figure 4-13
).
A time saving jump on cache is always taken after the second and any further occurrence
of the same cache jump instruction, unless an instruction, which has the fundamental
capability of changing the CSP register contents (JMPS, CALLS, RETS, TRAP, RETI),
or any standard interrupt has been processed during the period of time between two
following occurrences of the same cache jump instruction.
Figure 4-13
Cache Jump Instruction Pipelining
Particular Pipeline Effects
Since up to four different instructions are processed simultaneously, additional hardware
has been used in the CPU to consider all causal dependencies which may exist on
instructions in different pipeline stages without a loss of performance. This extra
hardware (i.e. for “forwarding” operand read and write values) resolves most of the
UED11126
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n+2
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TARGET
FETCH
DECODE
EXECUTE
WRITEBACK
1 Machine Cycle
1st Loop Iteration
...
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Cache Jmp
INJECT
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2
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Injection
Cache Jmp
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INJECT
TARGET
(
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1
I
Cache Jmp
Cache Jmp
I
...
n
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n+2
1
TARGET
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Cache Jmp
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TARGET
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Cache Jmp
Repeated Loop Iteration
Target Instruction
Injection of Cached
Содержание SDA 6000
Страница 3: ...Contents Overview...
Страница 21: ...Pin Description...
Страница 22: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 Pin Descriptions 2 3 Micronas 2 Pin Descriptions...
Страница 29: ...Architectural Overview...
Страница 33: ...C16X Microcontroller...
Страница 34: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 C16X Microcontroller 4 3 Micronas 4 C16X Microcontroller...
Страница 88: ...Interrupt and Trap Function...
Страница 122: ...System Control Configuration...
Страница 159: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 System Control Configuration 6 40 Micronas...
Страница 160: ...Peripherals...
Страница 282: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 Peripherals 7 124 Micronas...
Страница 283: ...Clock System...
Страница 284: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 Clock System 8 3 Micronas 8 Clock System...
Страница 288: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 Clock System 8 8 Micronas...
Страница 289: ...Sync System...
Страница 290: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 Sync System 9 3 Micronas 9 Sync System...
Страница 301: ...Display Generator...
Страница 302: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 Display Generator 10 3 Micronas 10 Display Generator...
Страница 348: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 Display Generator 10 50 Micronas...
Страница 349: ...D A Converter...
Страница 352: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 D A Converter 11 6 Micronas...
Страница 353: ...Slicer and Acquisition...
Страница 354: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 Slicer and Acquisition 12 3 Micronas 12 Slicer and Acquisition...
Страница 381: ...Register Overview...
Страница 398: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 Register Overview 13 20 Micronas...
Страница 399: ...Elelctrical Characteristics...
Страница 400: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 Electrical Characteristics 14 3 Micronas 14 Electrical Characteristics...
Страница 411: ...SDA 6000 PRELIMINARY DATA SHEET Version 2 1 Electrical Characteristics 14 14 Micronas...