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參數(shù)資料
| 型號： | AN1218 |
| 廠商： | 飛思卡爾半導體(中國)有限公司 |
| 英文描述： | HC05 to HC08 Optimization |
| 中文描述： | 以HC08的優(yōu)化HC05 |
| 文件頁數(shù)： | 20/56頁 |
| 文件大?。?/td> | 417K |
| 代理商： | AN1218 |
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Application Note
AN1218 Rev. 2
20
Data Movement
Why Improve the
MovementofData
in the CPU05
The most common CPU function is the transfer of data. Most
microcontroller-based systems spend the majority of their time moving
data from one location to the other. Many different addressing modes
are used to access and transfer bytes of data. If there was a way to
decrease the time it takes to transfer data, then the overall performance
of the system would be improved.
CPU05 moves data from one location to the next by first loading the
accumulator with the byte from the transfer source. Next, CPU05 stores
the byte from the accumulator to the transfer's destination. In this
manner all data must pass through the accumulator, thus making the
accumulator a bottleneck in data movement. The movement of the
contents of location $40 to location $60 with the CPU05 is illustrated in
Figure 7
.
CPU08 provides the new MOV instruction which bypasses the
accumulator. Using the MOV instruction, the CPU is instructed to take
the contents of the source location and directly place the data in the
destination. This is illustrated in
Figure 8
. There are four different
addressing modes special to the MOV instruction. Details of this
instruction are given below. .
LDA $40
#
$40
→ →
#
ACCA
STA $60
#
$60
← ←
Figure 7. Accumulator as a Bottleneck
MOV $40,$60
#
$40
↓
↓
#
$60
Figure 8. No Accumulator Bottleneck
F
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
n
.
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