1.現(xiàn)象

用戶(hù)反映在使用PCI-1230的I/O控制卡時(shí)，如果先給機(jī)臺(tái)上電（常用規(guī)格為24V），再按下計(jì)算機(jī)的啟動(dòng)開(kāi)關(guān)后，I/O控制卡的輸出端口控制的外設(shè)（電磁閥，繼電器）會(huì)有瞬間的變化(指示燈閃爍一下或氣閥突然動(dòng)作一下, 輸出的位號(hào)不定)。

2.原因分析

計(jì)算機(jī)在上電時(shí),主板會(huì)提供復(fù)位信號(hào)(RST#,低有效)到PCI設(shè)備，I/O控制卡的硬件設(shè)計(jì)會(huì)保證在復(fù)位信號(hào)有效期間使DO輸出處于截止?fàn)顟B(tài)(電流無(wú)法通過(guò)); 復(fù)位信號(hào)長(zhǎng)度與主板有關(guān),常見(jiàn)的不小于100ms; 下圖是PCI規(guī)范里面的復(fù)位時(shí)序:

 

計(jì)算機(jī)在上電后，會(huì)執(zhí)行BIOS程序，BIOS程序會(huì)通過(guò)讀寫(xiě)一定范圍的I/O空間來(lái)檢測(cè)即插即用(Plug and Play)外圍設(shè)備，包括主板內(nèi)置的設(shè)備與用戶(hù)另外增加的設(shè)備，比如數(shù)據(jù)采集卡，然后把相關(guān)的配置信息保存在CMOS芯片中提供給操作系統(tǒng)使用，之后才啟動(dòng)操作系統(tǒng)。

 

I/O控制卡輸出瞬變，是BIOS程序在檢測(cè)即插即用(Plug and Play)外圍設(shè)備期間對(duì)I/O空間的讀寫(xiě)造成的。

受影響的產(chǎn)品范圍：PCI-1230, PCI-1232, PCI-1234，PCI-9014, PCI-9016等使用了PCI I/O空間(I/O Space)進(jìn)行地址譯碼的設(shè)計(jì)。

3.解決方法

1) BIOS設(shè)置啟用PnP OS

在計(jì)算機(jī)開(kāi)機(jī)時(shí)，持續(xù)按住“Delete”鍵，進(jìn)入BIOS設(shè)置界面，然后進(jìn)入“Advanced”下面的“PCI / PnP”，點(diǎn)擊回車(chē)鍵，即“Enter”鍵，選擇“YES”后保存設(shè)置，再退出系統(tǒng)。如下圖所示：

如上圖的右邊描述，這樣設(shè)置的目的是在計(jì)算機(jī)啟動(dòng)時(shí)，BIOS只檢測(cè)和設(shè)置與系統(tǒng)引導(dǎo)相關(guān)的即插即用硬件設(shè)備，其它的硬件設(shè)備由操作系統(tǒng)來(lái)配置； 這樣保證了I/O控制卡在BIOS啟動(dòng)時(shí)不被檢測(cè)和設(shè)置、I/O控制卡的DO端口就不會(huì)有瞬間信號(hào)輸出。

2) 使用PCI Express接口控制卡

PCI Express接口的控制卡在設(shè)計(jì)時(shí)，全部使用存儲(chǔ)器控件(Memory Space)進(jìn)行地址譯碼，不會(huì)存在該問(wèn)題。

  3. 關(guān)于PnP OS

Setting the plug and play BIOS option (PNP OS) in CMOS Setup

When you start your computer, the basic input/output system (BIOS) checks (among other things) the system-specific settings that are stored in the complementary metal-oxide semiconductor (CMOS) chip. You can modify these settings as the system changes. 

To change the CMOS settings, you must enter CMOS Setup by pressing a specific key or a combination of keys during the initial startup sequence. For example, press DEL or CTRL+ALT+ESC during the startup. (The specific key combination that you press is typically indicated during startup as "Press to enter Setup".) 

After you have entered Setup, windows that display various options and settings appear. Some of these options are standard, while others are specific to the BIOS manufacturer. 

One of the CMOS settings is the PNP OS option. This setting tells BIOS how many devices to configure at startup. The table in "More Information" shows the effect of this option on the configuration of the motherboard devices. 

The original intent for designing this option was to give Microsoft Windows versions 95 and 98 more freedom to adjust hardware configurations. By default, these operating systems would never move a device configured at startup for fear of breaking a DOS driver. Later versions of Windows also typically leave BIOS-configured hardware alone, even if the BIOS placed the hardware in a less than optimal configuration. This is because moving such hardware frequently exposes latent bugs in the BIOS.

Setting	Description
PNP OS set to Yes	The BIOS configures only critical devices (for example, video, hard-disk, and key- Board). NOTE: In this mode, neither the BIOS nor Windows configures the motherboard devices at startup. Therefore, for these earlier computers, you must set PNP OS to No.
PNP OS set to No	The BIOS configures critical devices and all motherboard devices under the assumption that Windows cannot.
Former (legacy) ACPI BIOS PNP BIOS or APM BIOS	The PNP OS option is irrelevant. Windows (only Windows versions 98, Millennium Edition, 2000 and XP) uses the Advanced Configuration and Power Interface (ACPI) BIOS interface to configure motherboard devices and retrieve system information. NOTE: Although a system does have an ACPI BIOS, ACPI might have been disabled by Windows because of a bug in the ACPI BIOS. In this case, Windows will fall back to PNP BIOS and APM BIOS in read-only mode. Therefore, for any computer with a buggy ACPI BIOS, set PNP OS to No.

 

 

 

 

 

 

 

資料來(lái)源：

http://support.microsoft.com/kb/321779/en-us