ibcmd() writes the command bytes contained in the array commands to the bus. The number of bytes written from the array is specified by num_bytes. The ud argument is a board descriptor, and the board must be controller-in-charge. Most of the possible command bytes are declared as constants in the header files. In particular, the constants GTL, SDC, PPConfig, GET, TCT, LLO, DCL, PPU, SPE, SPD, UNL, UNT,and PPD are available. Additionally, the inline functions MTA(), MLA(), MSA(), and PPE_byte() are available for producing 'my talk address', 'my listen address', 'my secondary address', and 'parallel poll enable' command bytes respectively.
It is generally not necessary to call ibcmd(). It is provided for advanced users who want direct, low-level access to the GPIB bus.
The value of ibsta is returned.