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參數(shù)資料
| 型號： | DS87C550-FNL |
| 英文描述： | EPROM High-Speed Micro with A/D and PWM |
| 中文描述： | 存儲器高速微與A / D及PWM |
| 文件頁數(shù)： | 12/50頁 |
| 文件大?。?/td> | 763K |
| 代理商： | DS87C550-FNL |
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DS87C550
12 of 50
DATA MEMORY ACCESS CONTROL
Table 3
DME1
DME0
DATA MEMORY ADDRESS
0
0
0
1
MEMORY FUNCTION
External Data Memory *Default condition
Internal SRAM Data Memory
External Data Memory
Reserved
Internal SRAM Data Memory
Reserved - no external access
Read access to the status of lock bits
Reserved
0000h - FFFFh
0000h - 03FFh
0400h - FFFFh
Reserved
0000h - 03FFh
0400h – FFFBh
FFFCh
FFFDh - FFFFh
1
1
0
1
Notes on the status byte read at FFFCh with DME1, 0 = 1, 1: bits 2-0 reflect the programmed status of the
security lock bits LB2-LB0. They are individually set to a logic 1 to correspond to a security lock bit that
has been programmed. These status bits allow software to verify that the part has been locked before
running if desired. The bits are read only.
STRETCH MEMORY CYCLE
The DS87C550 allows software to adjust the speed of off-chip data memory and/or peripheral access by
adjusting the number of machine cycles it takes to execute a MOVX instruction. The micro is capable of
performing the MOVX in as little as two machine cycles. The on-chip SRAM uses this speed and any
MOVX instruction directed internally always uses two cycles. However, the time for the instruction
execution can be stretched for slower interface to external devices. This allows access to both fast
memory and slow memory or peripherals with no glue logic. Even in high-speed systems, it may not be
necessary or desirable to perform off-chip data memory access at full speed. In addition, there are a
variety of memory mapped peripherals such as LCDs or UARTs that are slow and require more time to
access.
The Stretch MOVX function is controlled by the MD2-MD0 SFR bits in the Clock Control Register
(CKCON.2-0) as described below. They allow the user to select a Stretch value between 0 and 7. A
Stretch of 0 will result in a two-machine cycle MOVX instruction. A Stretch of 7 will result in a MOVX
of 12 machine cycles. Software can dynamically change the stretch value depending on the particular
memory or peripheral being accessed. The default stretch of one allows the use of commonly available
SRAMs without dramatically lengthening the memory access times.
Note that the STRETCH MOVX function is slightly different in the DS87C550 than in earlier members
of the high-speed microcontroller family. In all members of this family (including the DS87C550),
increasing the stretch value from 0 to 1 causes setup and hold times to be increased by 1 crystal clock
each. In older members of the family, there is no further change in setup and hold times regardless of the
number of stretch cycles selected. In the DS87C550 however, when a stretch value of 4 or above is
selected, the timing of the interface changes dramatically to allow for very slow peripherals. First, the
ALE signal is increased by 1 machine cycle. This increases the address setup time into the peripheral by
this amount. Next, the address is held on the bus for one additional machine cycle, increasing the address
hold time by this amount. The Read or Write signal is then increased by a machine cycle. Finally, the data
is held on the bus (for a write cycle) one additional machine cycle, thereby increasing the data hold time
by this amount. For every Stretch value greater than 4, the setup and hold times remain constant, and only
the width of the read or write signal is increased.
On reset, the Stretch value will default to a 1, resulting in a three-cycle MOVX for any external access.
Therefore, the default off-chip RAM access is not at full speed. This is a convenience to existing designs
that may not have fast RAM in place. Internal SRAM access is always at full speed regardless of the
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| DS87C550-KCL | EPROM High-Speed Micro with A/D and PWM |
| DS87C550-QNL | EPROM High-Speed Micro with A/D and PWM |
| DS8820J | Line Receiver |
| DS8859AJ | LED Display Driver |
| DS8859AN | LED Display Driver |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| DS87C550-KCL | 制造商:DALLAS 制造商全稱:Dallas Semiconductor 功能描述:EPROM High-Speed Micro with A/D and PWM |
| DS87C550-QCL | 制造商:DALLAS 制造商全稱:Dallas Semiconductor 功能描述:EPROM High-Speed Micro with A/D and PWM |
| DS87C550-QCL+ | 功能描述:IC MCU EPROM ADC/PWM HS 68-PLCC RoHS:是 類別:集成電路 (IC) >> 嵌入式 - 微控制器， 系列:87C 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:260 系列:73S12xx 核心處理器:80515 芯體尺寸:8-位 速度:24MHz 連通性:I²C，智能卡，UART/USART，USB 外圍設(shè)備:LED，POR，WDT 輸入/輸出數(shù):9 程序存儲器容量:64KB（64K x 8） 程序存儲器類型:閃存 EEPROM 大小:- RAM 容量:2K x 8 電壓 - 電源 (Vcc/Vdd):2.7 V ~ 5.5 V 數(shù)據(jù)轉(zhuǎn)換器:- 振蕩器型:內(nèi)部 工作溫度:-40°C ~ 85°C 封裝/外殼:68-VFQFN 裸露焊盤 包裝:管件 |
| DS87C550-QCW | 制造商:Maxim Integrated Products 功能描述:DS87C550 WAIVERED FOR LS & MARKING - Rail/Tube |
| DS87C550-QNL | 功能描述:IC MCU EPROM ADC/PWM HS 68-PLCC RoHS:否 類別:集成電路 (IC) >> 嵌入式 - 微控制器， 系列:87C 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標準包裝:260 系列:73S12xx 核心處理器:80515 芯體尺寸:8-位 速度:24MHz 連通性:I²C，智能卡，UART/USART，USB 外圍設(shè)備:LED，POR，WDT 輸入/輸出數(shù):9 程序存儲器容量:64KB（64K x 8） 程序存儲器類型:閃存 EEPROM 大小:- RAM 容量:2K x 8 電壓 - 電源 (Vcc/Vdd):2.7 V ~ 5.5 V 數(shù)據(jù)轉(zhuǎn)換器:- 振蕩器型:內(nèi)部 工作溫度:-40°C ~ 85°C 封裝/外殼:68-VFQFN 裸露焊盤 包裝:管件 |
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