HOWTO: How to Set the ECP Mode Addressing on LPT Ports

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How to Address Up to 128 Separate I/O Devices from a VxD

The standard call for EscapeCommFunction is given as:

include vcomm.inc

VxDcall _VCOMM_EscapeCommFunction, <hPort, lFunc, \ 
   InData, <OFFSET32 OutData>>
or      eax, eax
jz      error_handler
				

Set hPort to the handle passed back from OpenComm, set lfunc to SETECPADDRESS, and set InData to a pointer to a buffer the first byte of which is the address to be set 0x00..0x7F.

How to Address Up to 128 Separate I/O Devices from a 32-bit Application

Please refer to the MSDN Library compact disc for the standard DeviceIoContol() function. Set hDevice to the device handle, set dwIoControlCode to SETECPADDRESS, and set lpInBuffer to a pointer to a buffer the first byte of which is the address 0x00..0x7F. Use GetLastError() to retrieve the error code if the function returns false.

Notes

The IEEE specification defines values 0x80..0xFF as pertaining to compression. You cannot use that from here. Values exceeding 0x7F will return error code IE_INVALIDPARAM.

If the port will support ECP mode, it will be set to that and the address transmitted.

If the port does not support ECP mode or is in reverse transfer currently, the error code IE_HARDWARE will be sent back.