Int 14 Fn 0A  - Mbbios - Write Buffer                                      [S]

   AH = 0Ah
   CX = count
   ES:DI -> buffer

Return: AX = status (see AH=03h)
   CX = unsent character count
   DI updated

Note:  the PACCOM version of MBBIOS does not use CX or ES:DI; instead, ES
     contains the segment of a buffer containing the packet to be sent,
     which by default will be freed once the packet has been sent.  Use
     AH=0Ch"MBBIOS" to allocate the buffer.

See Also: AH=01h,AH=0Bh"MBBIOS",AH=0Ch"MBBIOS",AH=19h"FOSSIL"

Format of PACCOM buffer:
Offset Size    Description
 00h 504 BYTEs data area
1F8h   WORD    length of data in data area
1FAh   BYTE    flags/status
       bit 7: don't discard buffer after transmitting data
       bit 6: buffer has been transmitted
1FBh   BYTE    reserved (0) for additional flags/status
1FCh   WORD    user data
1FEh   WORD    MBBIOS-internal pointer to next buffer