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mov     bx, [DeviceID]  ; device identifier
 
mov     ax, 1607h       ; Device Call Out
int     2fh             ; Multiplex Interrupt
 
Device Call Out (Interrupt 2Fh Function 1607h) directs an MS-DOS device
driver or TSR to provide information to the calling virtual device. Although
the BX register specifies a device identifier, other registers may be used
to specify the action to take.
 
Parameter  Description
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DeviceID   Specifies the device identifier for a virtual device.
 
Return Value
 
The return value depends on the specific action requested.
 
Comments
 
This function typically is used by a virtual device to communicate with the
driver or TSR that explicitly loaded the virtual device. It is up to the
virtual device to supply a correct device identifier and any other
parameters that specify what action to take. It is up to the driver or TSR
to monitor Interrupt 2Fh, and respond to the function appropriately.
 
A virtual device can call this function at any time, either in real mode or
after 386 enhanced-mode Windows has started.
 
 
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