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參數資料
| 型號： | DS89C450 |
| 英文描述： | RES,Wirewound,301Ohms,1+/-% Tol,-20,20ppm-TC,4427-Case |
| 中文描述： | 超高速閃存微控制器 |
| 文件頁數： | 26/48頁 |
| 文件大?。?/td> | 656K |
| 代理商： | DS89C450 |
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DS89C430/DS89C440/DS89C450 Ultra-High-Speed Flash Microcontrollers
26 of 48
External Memory
The DS89C430 executes external memory cycles for code fetches and read/writes of external program and data
memory. A nonpage external memory cycle is four times slower than the internal memory cycles (i.e., an external
memory cycle contains four system clocks). However, a page mode external memory cycle can be completed in
one, two, or four system clocks for a page hit and two, four, or eight system clocks for a page miss, depending on
user selection. The DS89C430 also supports a second page mode operation with a different external bus structure
that provides for fast external code fetches but uses four system clock cycles for data memory access.
External Program Memory Interface (Nonpage Mode)
Figure 7
shows the timing relationship for internal and external code fetches when CD1 and CD0 are set to 10b,
assuming the microcontroller is in nonpage mode for external fetches. Note that an external program fetch takes
four system clocks, and an internal program fetch requires only one system clock.
As illustrated in
Figure 7
, ALE is deasserted when executing an internal memory fetch. The DS89C430 provides a
programmable user option to turn on ALE during internal program memory operation. ALE is automatically enabled
for code fetch externally, independent of the setting of this option.
PSEN
is only asserted for external code fetches, and is inactive during internal execution.
Figure 7. External Program Memory Access (Nonpage Mode, CD1:CD0 = 10)
Internal Memory Cycles
C1
C2
C3
C4 C1 C2 C3 C4
XTAL1
ALE
Port 0
Port 2
PSEN
External Memory Cycle
External Memory Cycle
MSB Add MSB Add
LSB Add Data LSB Add Data
相關PDF資料 |
PDF描述 |
|---|---|
| DS907X | SipStik Connectors |
| DS9090K | 1-Wire Memory Evaluation Kit |
| DS9093A | iButton Key Ring Mounts |
| DS9093F | iButton Key Ring Mounts |
| DS9093N | iButton Key Ring Mounts |
相關代理商/技術參數 |
參數描述 |
|---|---|
| DS89C450+ENG | 制造商:Maxim Integrated Products 功能描述:MCU 8BIT CISC 64KB FLASH 5V 44TQFP - Trays |
| DS89C450+ENL | 制造商:Maxim Integrated Products 功能描述:MCU 8BIT CISC 64KB FLASH 5V 44TQFP - Trays |
| DS89C450+MNG | 制造商:Maxim Integrated Products 功能描述:MCU 8BIT CISC 64KB FLASH 5V 40PDIP - Rail/Tube |
| DS89C450+MNL | 制造商:Maxim Integrated Products 功能描述:MCU 8BIT CISC 64KB FLASH 5V 40PDIP - Rail/Tube |
| DS89C450+QNL | 制造商:Maxim Integrated Products 功能描述:MICRO HI SPD 44PLCC 64K IND PB-FREE - Rail/Tube |
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