1.現(xiàn)象

用戶反映在使用PCI-1230的I/O控制卡時，如果先給機臺上電（常用規(guī)格為24V），再按下計算機的啟動開關后，I/O控制卡的輸出端口控制的外設（電磁閥，繼電器）會有瞬間的變化(指示燈閃爍一下或氣閥突然動作一下, 輸出的位號不定)。

2.原因分析

計算機在上電時,主板會提供復位信號(RST#,低有效)到PCI設備，I/O控制卡的硬件設計會保證在復位信號有效期間使DO輸出處于截止狀態(tài)(電流無法通過); 復位信號長度與主板有關,常見的不小于100ms; 下圖是PCI規(guī)范里面的復位時序:

 

計算機在上電后，會執(zhí)行BIOS程序，BIOS程序會通過讀寫一定范圍的I/O空間來檢測即插即用(Plug and Play)外圍設備，包括主板內(nèi)置的設備與用戶另外增加的設備，比如數(shù)據(jù)采集卡，然后把相關的配置信息保存在CMOS芯片中提供給操作系統(tǒng)使用，之后才啟動操作系統(tǒng)。

 

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

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)進行地址譯碼的設計。

3.解決方法

1) BIOS設置啟用PnP OS

在計算機開機時，持續(xù)按住“Delete”鍵，進入BIOS設置界面，然后進入“Advanced”下面的“PCI / PnP”，點擊回車鍵，即“Enter”鍵，選擇“YES”后保存設置，再退出系統(tǒng)。如下圖所示：

如上圖的右邊描述，這樣設置的目的是在計算機啟動時，BIOS只檢測和設置與系統(tǒng)引導相關的即插即用硬件設備，其它的硬件設備由操作系統(tǒng)來配置； 這樣保證了I/O控制卡在BIOS啟動時不被檢測和設置、I/O控制卡的DO端口就不會有瞬間信號輸出。

2) 使用PCI Express接口控制卡

PCI Express接口的控制卡在設計時，全部使用存儲器控件(Memory Space)進行地址譯碼，不會存在該問題。

  3. 關于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.

 

 

 

 

 

 

 

資料來源：

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