參數(shù)資料
型號(hào)： DS89C420
英文描述： Ultra-High-Speed Microcontroller
中文描述： 超高速微控制器
文件頁(yè)數(shù)： 23/59頁(yè)
文件大?。?/td> 539K
代理商： DS89C420
DS89C420
23 of 59
External Data Memory Interface in Non-Page Mode Operation
Just like the program memory cycle, the external data memory cycle is four times slower than the internal
data memory cycle in non-page mode. A basic internal memory cycle contains one system clock and a
basic external memory cycle contains four system clocks for non-page mode operation.
The DS89C420 allows software to adjust the speed of external data memory access by stretching the
memory bus cycle. CKCON (8Eh) provides an application-selectable stretch value for this purpose.
Software can change the stretch value dynamically by changing the setting of CKCON.2–CKCON.0.
Table 6 shows the data memory cycle stretch values and their effects on the external MOVX-memory bus
cycle and the control signal pulse width in terms of the number of oscillator clocks. A stretch machine
cycle always contains four system clocks.
Table 6. Data Memory Cycle Stretch Values
RD
/
WR
PULSE WIDTH (IN NUMBER OF OSCILLATOR CLOCKS)
4X/2X, CD1,
CD0 = 100
CD0 = 000
0.5
1
1
2
2
4
3
6
4
8
5
10
6
12
7
14
MD2:MD0
STRETCH
CYCLES
4X/2X, CD1,
4X/2X, CD1,
CD0 = X10
2
4
8
12
16
20
24
28
4X/2X, CD1,
CD0 = X11
2048
4096
8192
12288
16384
20480
24576
28672
000
001
010
011
100
101
110
111
0
1
2
3
7
8
9
10
As shown in Table 6, the stretch feature supports eight stretched external data-memory access cycles that
can be categorized into three timing groups. When the stretch value is cleared to 000b, there is no stretch
on external data memory access and a MOVX instruction is completed in two basic memory cycles.
When the stretch value is set to 1, 2, or 3, the external data-memory access is extended by 1, 2, or 3
stretch machine cycles, respectively. Note that the first stretch value does not result in adding four system
clocks to the
RD
/
WR control signals. This is because the first stretch uses one system clock to create
additional setup time and one system clock to create additional address hold time. When using very slow
RAM and peripherals, a larger stretch value (4–7) can be selected. In this stretch category, one stretch
machine cycle (4 system clocks) is used to stretch the ALE pulse width, one stretch machine cycle is used
to create additional setup, one stretch machine cycle is used to create additional hold time, and one stretch
machine cycle is added to the
RD
or WR strobes.
Figures 5 and 6 illustrate the timing relationship for external data-memory access in full speed (stretch
value = 0), in the default stretch setting (stretch value =1), and slow data-memory accessing
(stretch value = 4) when the system clock is in divide by one mode (CD1:CD0 = 10b).
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
DS89C420_02 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:Ultra-High-Speed Microcontroller
DS89C420_05 制造商:MAXIM 制造商全稱:Maxim Integrated Products 功能描述:Ultra-High-Speed Microcontroller
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DS89C420-ECS 功能描述:IC MCU 50MHZ ULTRA HS 44-TQFP RoHS:否 類別:集成電路 (IC) >> 嵌入式 - 微控制器， 系列:89C 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)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(chǔ)器容量:64KB（64K x 8） 程序存儲(chǔ)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
DS89C420-ENG 功能描述:IC MCU ULTRA 25MHZ HP 44-TQFP RoHS:否 類別:集成電路 (IC) >> 嵌入式 - 微控制器， 系列:89C 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)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(chǔ)器容量:64KB（64K x 8） 程序存儲(chǔ)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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