INT 21 - PC/TCP IPCUST.SYS - WRITE CONFIGURATION DATA
AH = 40h
BX = handle for character device "$IPCUST"
CX = number of bytes to write
DS:DX -> buffer for configuration data (AH=3Fh"IPCUST")
Return: CF clear if successful
AX = number of bytes actually written
CF set on error
AX = error code (05h,06h) (see AH=59h)
Notes:  if less than the entire data is read or written, the next read/write
continues where the previous one ended; IOCTL calls AX=4402h and
AX=4403h both reset the location at which the next operation starts
to zero
the data pointer is also reset to zero if the previous read or write
reached or exceeded the end of the data, when the current function
is read and the previous was write, or vice versa
SeeAlso: AX=4402h"IPCUST"

See also: 213F

2140 - PC/TCP IPCUST.SYS - WRITE CONFIGURATION DATA