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參數(shù)資料
| 型號： | DS87C550 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | EPROM High-Speed Micro with A/D and PWM(帶 A/D 和 PWM的EPROM/ROM高速微控制器) |
| 中文描述： | 存儲器高速微與A / D及PWM（帶A / D轉(zhuǎn)換和脈寬調(diào)制的存儲器/ ROM的高速微控制器） |
| 文件頁數(shù)： | 12/27頁 |
| 文件大?。?/td> | 119K |
| 代理商： | DS87C550 |
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APPLICATION NOTE 78
030998 12/27
CLOCK CONTROL AND STATUS BIT SUMMARY
Table 3
BIT
NAME
LOCATION
FUNCTION
RESET
WRITE ACCESS
XT/RG
EXIF.3
Crystal/Ring Clock Source Select.
0= Select ring oscillator as clock source.
1= Select crystal or external clock as clock
source.
1
0 anytime;
1 when XTUP=1
and XTOFF=0
RGMD
EXIF.2
Ring Oscillator Mode Status.
0= Crystal or external clock is current clock
source.
1= Ring oscillator is current clock source.
0
None
RGSL
EXIF.1
Ring Oscillator Select, Stop Mode.
0= Crystal or external clock will be the clock
source when resuming from Stop mode.
1= Ring oscillator will be the clock source
when resuming from Stop mode.
Note: Upon completion of crystal warm up
period, device will switch to clock source
designated by XT/RG bit.
Unchanged
except after pow-
er–on reset, when
it is cleared to 0.
Unrestricted
XTOFF
PMR.3
Crystal Oscillator Disable.
0= Crystal oscillator is enabled.
1= Crystal oscillator is disabled. Device is
operating from ring oscillator.
0
0 anytime;
1 when XT/RG=0
XTUP
STATUS.4
Crystal Oscillator Warm Up Status.
0= Oscillator warm up still in progress.
1= Oscillator warm up complete.
1
None
CRYSTAL OSCILLATOR STARTUP DELAY
When power is applied to a crystal oscillator after a
period of non–operation, a short period of time is
required before the amplitude of the pulse is sufficient to
provide a stable clock source. This can result in missed
or corrupted clock signals, possibly disrupting proces-
sor operation. To ensure a valid clock signal, the
DS87C5x0 uses a crystal startup counter to detect
65,536 oscillations of the external crystal or clock oscil-
lator before allowing the device to resume operation.
This means that devices utilizing slower crystals will
have longer crystal startup times. The crystal startup
counter is more sensitive than the internal clock cir-
cuitry, and uses the count of both bad and good pulses
to determine the warm–up period. The counter value
was chosen to allow the majority of crystals enough time
to stabilize before releasing the device to run off the
external crystal. The counter is reset anytime the
XTOFF bit is cleared.
The status of the crystal startup counter can be deter-
mined by reading the Crystal Oscillator Warm Up Status
Bit, XTUP (STATUS.4). Note that this bit will always be
set upon a power–on reset, because the counter must
time out before the device will resume operation. For the
same reason, this bit will also be set when resuming
from Stop mode with the XT/RG bit set to 1. When
switching from the ring oscillator to the crystal oscillator,
the XTUP bit can be used to tell when the crystal has
stabilized. Attempts to switch to the external crystal
before the XTUP bit has been set will be disregarded.
SWITCHING BETWEEN CLOCK SOURCES
On occasion the device may wish to switch between the
ring oscillator and crystal oscillator. The device can
switch to the ring oscillator at any time as there is no
start up delay associated with the ring oscillator. Clear-
ing the Crystal Oscillator/Ring Oscillator Select Bit,
XT/RG (EXIF.3) will enable the ring oscillator. If there is
no expectation that the crystal oscillator will be needed
soon, the crystal oscillator can be disabled by setting the
Crystal Oscillator Disable Bit, XTOFF (PMR.3). This will
provide a significant power savings. Note that clearing
the XT/RG bit does not automatically disable the crystal
amplifier.
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| 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 |
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