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参数资料
| 型号： | AT87251G2D-SLSUM |
| 厂商： | ATMEL CORP |
| 元件分类： | 微控制器/微处理器 |
| 英文描述： | B/16-BIT MICROCONTROLLER WITH SERIAL COMMUNICATION INTERFACES |
| 中文描述： | 16-BIT, OTPROM, 24 MHz, MICROCONTROLLER, PQCC44 |
| 封装： | GREEN, PLASTIC, LCC-44 |
| 文件页数： | 21/76页 |
| 文件大小： | 1175K |
| 代理商： | AT87251G2D-SLSUM |
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21
AT/TSC8x251G2D
4135D–8051–08/05
Instruction Set
Summary
This section contains tables that summarize the instruction set. For each instruction
there is a short description, its length in bytes, and its execution time in states (one state
time is equal to two system clock cycles). There are two concurrent processes limiting
the effective instruction throughput:
Instruction Fetch
Instruction Execution
Table 20 to Table 32 assume code executing from on-chip memory, then the CPU is
fetching 16-bit at a time and this is never limiting the execution speed.
If the code is fetched from external memory, a pre-fetch queue will store instructions
ahead of execution to optimize the memory bandwidth usage when slower instructions
are executed. However, the effective speed may be limited depending on the average
size of instructions (for the considered section of the program flow). The maximum aver-
age instruction throughput is provided by Table 14 depending on the external memory
configuration (from Page Mode to Non-Page Mode and the maximum number of wait
states). If the average size of instructions is not an integer, the maximum effective
throughput is found by pondering the number of states for the neighbor integer values.
Table 14.
Minimum Number of States per Instruction for given Average Sizes
If the average execution time of the considered instructions is larger than the number of
states given by Table 14, this larger value will prevail as the limiting factor. Otherwise,
the value from Table 14 must be taken. This is providing a fair estimation of the execu-
tion speed but only the actual code execution can provide the final value.
Notation for Instruction
Operands
Table 15 to Table 19 provide notation for Instruction Operands.
Table 15.
Notation for Direct Addressing
Average size
of Instructions
(bytes)
Page Mode
(states)
Non-page Mode (states)
0 Wait
State
1 Wait
State
2 Wait States 3 Wait States 4 Wait States
1
1
2
3
4
5
6
2
2
4
6
8
10
12
3
3
6
9
12
15
18
4
4
8
12
16
20
24
5
5
10
15
20
25
30
Direct
Address
Description
C251
C51
dir8
A direct 8-bit address. This can be a memory address (00h-7Fh) or a
SFR address (80h-FFh). It is a byte (default), word or double word
depending on the other operand.
3
3
dir16
A 16-bit memory address (00:0000h-00:FFFFh) used in direct
addressing.
3
–
相关PDF资料 |
PDF描述 |
|---|---|
| AT80251G2D | B/16-BIT MICROCONTROLLER WITH SERIAL COMMUNICATION INTERFACES |
| AT80251G2D-3CSUM | B/16-BIT MICROCONTROLLER WITH SERIAL COMMUNICATION INTERFACES |
| AT80251G2D-RLTUL | B/16-BIT MICROCONTROLLER WITH SERIAL COMMUNICATION INTERFACES |
| AT80251G2D-RLTUM | CONNECTORS, INDUSTRIAL; SERIES:97/MS; CONNECTOR TYPE:CIRCULAR; ER 3C 3#8 SKT RECP BOX |
| AT80251G2D-SLSUL | ER 3C 3#8 SKT RECP BOX |
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| AT875LTS44 | 制造商:POSEICO 制造商全称:POSEICO 功能描述:PHASE CONTROL THYRISTOR |
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| AT-879/ARC | 制造商: 功能描述: 制造商:undefined 功能描述: |
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