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參數(shù)資料
| 型號(hào)： | DS87C530-QNL |
| 英文描述： | EPROM MICRO WITH REAL TIME CLOCK |
| 中文描述： | 微型存儲(chǔ)器與實(shí)時(shí)時(shí)鐘 |
| 文件頁數(shù)： | 16/40頁 |
| 文件大?。?/td> | 435K |
| 代理商： | DS87C530-QNL |
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DS87C530
022197 16/40
(High Interrupt Priority; STATUS.6) or LIP (Low Interrupt
Priority; STATUS.5) is high, then the corresponding
level is in service.
Software should not rely on a lower priority level inter-
rupt source to remove PMM (Switchback) when a
higher level is in service. Check the current priority ser-
vice level before entering PMM. If the current service
level locks out a desired Switchback source, then it
would be advisable to wait until this condition clears
before entering PMM.
Alternately, software can prevent an undesired exit from
PMM by entering a low priority interrupt service level
before entering PMM. This will prevent other low priority
interrupts from causing a Switchback.
Status also contains information about the state of the
serial ports. Serial Port Zero Receive Activity (SPRA0;
STATUS.0) indicates a serial word is being received on
Serial Port 0 when this bit is set to a 1. Serial Port Zero
Transmit Activity (SPTA0; STATUS.1) indicates that the
serial port is still shifting out a serial transmission. STA-
TUS.2 and STATUS.3 provide the same information for
Serial Port 1, respectively. These bits should be
interrogated before entering PMM1 or PMM2 to ensure
that no serial port operations are in progress. Changing
the clock divisor rate during a serial transmission or
reception will corrupt the operation.
Crystal/Ring Operation
The DS87C530 allows software to choose the clock
source as an independent selection from the instruction
cycle rate. The user can select crystal–based or ring
oscillator–based operation under software control.
Power–on reset default is the crystal (or external clock)
source. The ring may save power depending on the
actual crystal speed. To save still more power, software
can then disable the crystal amplifier. This process
requires two steps. Reversing the process also requires
two steps.
The XT/RG bit (EXIF.3) selects the crystal or ring as the
clock source. Setting XT/RG = 1 selects the crystal. Set-
ting XT/RG = 0 selects the ring. The RGMD (EXIF.2) bit
serves as a status bit by indicating the active clock
source. RGMD = 0 indicates the CPU is running from
the crystal. RGMD = 1 indicates it is running from the
ring. When operating from the ring, disable the crystal
amplifier by setting the XTOFF bit (PMR.3) to a 1. This
can only be done when XT/RG = 0.
When changing the clock source, the selection will take
effect after a one instruction cycle delay. This applies to
changes from crystal to ring and vise versa. However,
this assumes that the crystal amplifier is running. In
most cases, when the ring is active, software previously
disabled the crystal to save power. If ring operation is
being used and the system must switch to crystal opera-
tion, the crystal must first be enabled. Set the XTOFF bit
to a 0. At this time, the crystal oscillation will begin. The
DS87C530 then provides a warm–up delay to make cer-
tain that the frequency is stable. Hardware will set the
XTUP bit (STATUS.4) to a 1 when the crystal is ready for
use. Then software should write XT/RG to a 1 to begin
operating from the crystal. Hardware prevents writing
XT/RG to a 1 before XTUP = 1. The delay between
XTOFF = 0 and XTUP = 1 will be 65,536 crystal clocks in
addition to the crystal cycle startup time.
Switchback has no effect on the clock source. If soft-
ware selects a reduced clock divider and enables the
ring, a Switchback will only restore the divider speed.
The ring will remain as the time base until altered by soft-
ware. If there is serial activity, Switchback usually
occurs with enough time to create proper baud rates.
This is not true if the crystal is off and the CPU is running
from the ring. If sending a serial character that wakes
the system from crystaless PMM, then it should be a
dummy character of no importance with a subsequent
delay for crystal startup.
The following table is a summary of the bits relating to
PMM and its operation. The flow chart below illustrates
a typical decision set associated with PMM.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| DS87C550 | EPROM High-Speed Micro with A/D and PWM |
| DS87C550-QCL | EPROM High-Speed Micro with A/D and PWM |
| DS87C550-FCL | EPROM High-Speed Micro with A/D and PWM |
| DS87C550-FNL | EPROM High-Speed Micro with A/D and PWM |
| DS87C550-KCL | EPROM High-Speed Micro with A/D and PWM |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| DS87C530-QNL+ | 功能描述:8位微控制器 -MCU EPROM MCU w/RTC RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時(shí)鐘頻率:50 MHz 程序存儲(chǔ)器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風(fēng)格:SMD/SMT |
| DS87C530Z+ECL | 制造商:Maxim Integrated Products 功能描述:MICRO OTP RTC 33MHZ 52P TQFP PB-FRR - Trays |
| DS87C550 | 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-FCL | 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-FNL | 制造商:DALLAS 制造商全稱:Dallas Semiconductor 功能描述:EPROM High-Speed Micro with A/D and PWM |
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