National Instruments NI-VXI - Manual (Page 60)

Chapter 3 Software Overview
NI-VXI User Manual 3-22 © National Instruments Corporation
WSSnoResp ()
WSSnoResp sets the WR bit so that it is ready to accept any further
Word Serial commands. The WSScmd interrupt handler should call
WSSnoResp after processing a Word Serial command (it calls
WSSsendResp for a Word Serial query, which requires a response).
WSSrd (buf, count, modevalue)
WSSrd is the buffer read function. WSSrd receives a specified number
of bytes from a VXI message-based Commander device and places the
bytes into a memory buffer, using the VXIbus Byte Transfer Protocol.
The process involves setting the DIR and WR bits on the local CPU
Response register and building a buffer out of data bytes received via a
series of Byte Available (BAV) Word Serial commands. When
WSSrd
reaches the specified count or an END bit, or an error occurs, it calls
the
WSSrd interrupt handler with the status of the call. It clears the DIR
bit before setting the WR on the last byte of transfer.
WSSsendResp (response)
WSSsendResp responds to a Word Serial Protocol query from a VXI
message-based Commander device. The WSScmd interrupt handler calls
this function to respond to a Word Serial query. If a previous response
has not been read yet, a
WSSsendResp call generates a Multiple Query
Error (MQE). Otherwise, it writes a response value to the Data Low
register and sets the RR bit is. It also sets the WR bit so that it is ready
to accept any further Word Serial commands.
WSSwrt (buf, count, modevalue)
WSSwrt sends a specified number of bytes to a VXI message-based
Commander device, using the VXIbus Byte Transfer Protocol. The
process involves setting the DOR and WR bits in the local Response
register and responding to a series of Byte Request (BREQ) Word
Serial commands. When the data output completes or an error occurs,
WSSwrt calls its interrupt handler with the status of the call. Before
responding to the last byte of the write, it clears DOR to prevent
another BREQ from being sent before the application is able to handle
the BREQ properly.