Example Fifo acquisition mode

Programming	FIFO Mode

FIFO mode

In normal applications the FIFO mode will run in a loop and process one buffer after the other. There are a few special commands and reg- isters for the FIFO mode:

Register		Value	Direction	Description
SPC_COMMAND		0	w	Command register. Allowed values for FIFO mode are listed below
	SPC_FIFOSTART	12	Starts the FIFO mode and waits for the first interrupt

	SPC_FIFOWAIT	13	Waits for the next buffer interrupt

	SPC_STOP	20	Stops the FIFO mode

The start command and the wait command both wait for the signal from the driver that the next buffer has to be processed. This signal is generated by the driver on receiving an interrupt from the hardware. While waiting none of these commands waiste cpu power (no polling mode). If for any reason the signal is not coming from the hardware (e.g. trigger is not found) the FIFO mode must be stopped from a second task with a stop command.

This handshake command tells the driver that the application has finished it’s work with the software buffer. The both commands

SPC_FIFOWAIT (SPC_FIFOSTART) and SPC_FIFO_BUFFERS form a simple but powerful handshake protocol between application software and board driver.

Register	Value	Direction	Description
SPC_FIFO_BUFREADY	60050	w	FIFO mode handshake. Application has finsihed with that buffer. Value is index of buffer

Backward compatibility: This register replaces the formerly known SPC_FIFO_BUFREADY0 ...

SPC_FIFO_BUFREADY15 commands. It has the same functionality but can handle more FIFO buffers. For back- ward compatibility the older commands still work but are still limited to 16 buffers.

This example shows the main loop of a FIFO acquisition. The example is a part of the FIFO examples that are available for each board on CD. The example simply counts the buffers when it receives a new buffer from the driver and returns control immideately back to the driver.

FIFO acquisition example:

nBufIdx = 0; lBufCount = 0; lCommand = SPC_FIFOSTART;

printf ("Start\n"); do

{

nErr = SpcSetParam (hDrv, SPC_COMMAND, lCommand); lCommand = SPC_FIFOWAIT;

//----- perform any data calculation or hard disk recording (in example only counting buffers)-----

printf ("FIFO Buffer %ld\n", lBufCount++);

//----- buffer is ready -----

SpcSetParam (hDrv, SPC_FIFO_BUFREADY, nBufIdx);

//----- next Buffer -----

nBufIdx++;

if (nBufIdx == MAX_BUF) nBufIdx = 0;

}

while (nErr == ERR_OK);

Data organization

When using FIFO mode data in memory is organized in some cases a little bit different then in standard mode. This is a result of the internal hardware structure of the board. The organization of data is depending on the activated channels:

Ch0

Ch1

Ch2

Ch3

Ch4

Ch5

Ch6

Ch7

Sample ordering in FIFO buffer

A10

A11

A12

A13

A14

A15

The samples are re-named for better readability. A0 is sample 0 of channel 0, C4 is sample 4 of channel 2, ...

56	MC.31xx Manual

Programming

FIFO mode

Register

SPC_FIFOSTART

SPC_FIFOWAIT

Register

SPC_FIFO_BUFREADY

Example FIFO acquisition mode

FIFO acquisition example:

Data organization