Function 4402h Receive Control Data from Character Device

mov bx, Handle ;handle of device

mov cx, MaxBytes ;maximum amount of data to receive

mov dx, seg Buffer

mov ds, dx

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

mov ax, 4402h ;Receive Control Data from Character Device

int 21h

jc error_handler ;carry set means error

mov ActualBytes, ax ;number of bytes received

Receive Control Data from Character Device (Function 4402h) reads control information of any length and format from a character-device driver. The format of the information is device-specific and does not follow any standard.

Parameters

Handle

Identifies the device to receive information from.

MaxBytes

Specifies the maximum number of bytes to read.

Buffer

Points to the buffer to receive the data read from the device. The buffer must be at least as large as MaxBytes.

Return Value

If the function is successful, the carry flag is clear, the buffer is filled in with the requested information, and the AX register contains the number of bytes received. 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 Send Control Data to Character Device (Function 4403h). 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.