请教版主一个问题

天嵌科技出品--WinCE完全开发手册(V2.1)_20091210.pdf中有一段GPIO的测试代码，讲的是将物理地址映射成虚拟地址：
VirtualCopy((PVOID)v_pIOPregs, (PVOID)(S3C2440A_BASE_REG_PA_IOPORT >> 8), sizeof(S3C2440A_IOPORT_REG), PAGE_PHYSICAL | PAGE_READWRITE | PAGE_NOCACHE)
为什么其中的物理地址要向右偏移8位呢？
请版主给出详细的解释，谢谢！

哪个高手帮我解决这个问题呀？！

This function dynamically maps a virtual address to a physical address by creating a new page-table entry. Terminate the mapping by calling VirtualFree.

BOOL VirtualCopy(
LPVOID lpvDest,
LPVOID lpvSrc,
DWORD cbSize,
DWORD fdwProtect
);Parameters
lpvDest
[in] Pointer to the destination memory, which must be reserved.
lpvSrc
[in] Pointer to committed memory.
cbSize
[in] Size, in bytes, of the region. The allocated pages include all pages containing one or more bytes in the range from lpAddress to lpAddress+cbSize. This means that a 2-byte range straddling a page boundary causes both pages to be included in the allocated region.


fdwProtect
[in] Type of access protection. If the pages are being committed, any one of a number of flags can be specified, along with the PAGE_GUARD and PAGE_NOCACHE, protection modifier flags. The following table shows the flags that can be specified.
Value Description
PAGE_READONLY              Enables read access to the committed region of pages. An attempt to write to the committed region results in an access violation. If the system differentiates between read-only access and execute access, an attempt to execute code in the committed region results in an access violation.
PAGE_READWRITE Enables both read and write access to the committed region of pages.
PAGE_EXECUTE           Enables execution access to the committed region of pages. An attempt to read or write to the committed region results in an access violation.
PAGE_EXECUTE_READ Enables execute and read access to the committed region of pages. An attempt to write to the committed region results in an access violation.
PAGE_EXECUTE_READWRITE Enables execute, read, and write access to the committed region of pages.
PAGE_GUARD              Pages in the region become guard pages. Any attempt to read from or write to a guard page causes the operating system to raise the STATUS_GUARD_PAGE exception and turn off the guard page status. Guard pages thus act as a one-shot access alarm.
The PAGE_GUARD flag is a page protection modifier. An application uses it with one of the other page protection flags, with one exception: it cannot be used with PAGE_NOACCESS.

When an access attempt leads the operating system to turn off guard page status, the underlying page protection takes over.

If a guard page exception occurs during a system service, the service typically returns a failure status indicator.

PAGE_NOACCESS         Disables all access to the committed region of pages. An attempt to read from, write to, or execute in the committed region results in an access violation exception, called a general protection (GP) fault.
PAGE_NOCACHE          Allows no caching of the committed regions of pages. The hardware attributes for the physical memory should be specified as no cache. It is useful for device drivers; when, for example, mapping a video frame buffer with no caching. This flag is a page protection modifier and is valid only when used with one of the page protections other than PAGE_NOACCESS.
PAGE_PHYSICAL         Used to map a physical memory region. When using this flag, divide the physical address — that is, lpvSrc — by 256. Memory mapped with PAGE_PHYSICAL is not freed until the device is rebooted. Calling VirtualFree will not free this mapped physical memory. PAGE_PHYSICAL is intended for use with dedicated hardware buffers, so it cannot be freed after being mapped.
上面最后一条最关键，除以256，也就是右移8位。