Function 4403h Send Control Data to Character Device

mov bx, Handle ;handle of device

mov cx, MaxBytes ;maximum number of bytes to send

mov dx, seg Buffer

mov ds, dx

mov dx, offset Buffer ;ds:dx points to buffer with data to send

mov ax, 4403h ;Send Control Data to Character Device

int 21h

jc error_handler ;carry set means error

mov ActualBytes, ax ;number of bytes sent

Send Control Data to Character Device (Function 4403h) writes control information of any length and format to a character-device driver. The format of the information is device-specific and does not follow any standard.

Parameters

Handle

Identifies the device to send information to.

MaxBytes

Specifies the number of bytes to write.

Buffer

Points to the buffer that contains the data to write to the device.

Return Value

If the function is successful, the carry flag is clear and the AX register contains the number of bytes sent. Otherwise, the carry flag is set and the AX register contains an error value, which may be one of the following:

Value

Name

0001h	ERROR_INVALID_FUNCTION
0005h	ERROR_ACCESS_DENIED
0006h	ERROR_INVALID_HANDLE
000Dh	ERROR_INVALID_DATA

Comment

Character-device drivers are not required to support this function or Receive Control Data from Character Device (Function 4402h). A program should use Get Device Data (Function 4400h) and examine bit 14 in the device-status value to ensure that the device driver can process control data.