National Instruments NI-VXI - page 54

Chapter 3 Software Overview
NI-VXI User Manual 3-16 © National Instruments Corporation
(DIR, DOR, WR, RR, and ERR*) are done automatically within the
functions as required.
Figure 3-2 provides a graphical overview of the Servant Word Serial
functions.
ERROR
Hardware
WSScmdHandler
NI-VXI base Interrupt Service Routine (ISR)
WSSenable()
WSSdisable()
SetWSScmdHandler()
GetWSScmdHandler()
DefaultWSScmdHandler()
Read Command
WSSLcmdHandlerWSSrdHandler WSSEcmdHandlerWSSwrtHandler
SetWSSwrtHandler()
GetWSSwrtHandler()
DefaultWSSwrtHandler()
SetWSSrdHandler()
GetWSSrdHandler()
DefaultWSSrdHandler()
SetWSSLcmdHandler()
GetWSSLcmdHandler()
DefaultWSSLcmdHandler()
SetWSSLcmdHandler()
GetWSSLcmdHandler()
DefaultWSSLcmdHandler()
WSS? WSSL? WSSE?
if write pending and cmd is
BREQ respond with next byte
if done 
call WSSwrtHandler with 
status set WR and exit
else if read pending and cmd
is BAV store byte in buffer
if done
call WSSrdHandler with
status set WR and exit
else call WSScmdHandler 

Local VXI Communication Registers
Write Data
Low High Ext
Read Data
Low High
Response
WR RR ERR*
WSSsendResp()
WSSLsendResp()
WSSwrt()
WSSrd()
NI-VXI
Software
User
Application
User
ISRs
Word Serial
Processor
RespProtError()
GenProtError()
(uint16)cmd
(uint16)cmd
(uint32)cmd
(uint16)cmdExt, (uint32)cmd
(int16)status, (uint32)count (int16)status, (uint32)count
WSSnoResp()
WSSLnoResp()
Figure 3-2. NI-VXI Servant Word Serial Model
The following paragraphs describe the Servant Word Serial, Longword
Serial, and Extended Longword Serial Protocol functions. The
descriptions are grouped by functionality and are presented at a
functional level describing the operation of each of the functions.