參數(shù)資料
型號(hào): THS1403EVM
廠商: Texas Instruments, Inc.
英文描述: THS1403EVM(THS1403評(píng)估板)
中文描述: THS1403EVM(THS1403評(píng)估板)
文件頁(yè)數(shù): 29/39頁(yè)
文件大小: 523K
代理商: THS1403EVM
Read Block Function
3-12
3.3.4
Read Block Function
void ths140x_rblock(void *pData, unsigned long ulCount,
void (*callback) (void *));
This function starts a read block transfer from the THS14xx to the DSP.
pData
points to the destination memory. The results will be stored in 32–bit words.
The THS14xx has 14-bit outputs. The output is not sign extended. Sign exten-
sion must be performed by the signal-processing algorithm.
If the routine is used with the FIFO, care must be taken to avoid a FIFO overrun
condition. Such a condition can happen, if the dc_rblock function is called over
and over again in a callback function to establish continuous conversion and
if the ulCount number is not an integer multiple of the FIFO trigger level. In this
case, the FIFO will fill up quickly because (ulCount modulo FIFO trigger level)
number of samples will be left in the FIFO after every block transfer.
If a FIFO overrun occurs, the FIFO must be reset by clearing the FIFO reset
bit within the THS14F0x control word before another block transfer is initiated.
Otherwise the callback function will never be executed.
3.3.5
Interrupt Service Routine
The THS14xx data converter example uses one interrupt service routine for
both FIFO and nonFIFO devices. The interrupt service routine is called upon
the end of a DMA transfer.
If a FIFO device (THS14F03 or THS14F01) is used, the DMA transfer count
is set to the trigger level of the FIFO. Every time the number of samples in the
FIFO reaches the trigger level, a short DMA burst is triggered followed by an
interrupt. The interrupt service routine checks if there are samples left in the
block transfer and sets up a new DMA burst, if necessary.
If a non-FIFO device (THS1408, THS1403, THS1401) is used, the DMA trans-
fer count is set to the number of samples in the block transfer. The DMA must
be synchronized with the master clock of the ADC by connecting the ADC mas-
ter clock to the EXT_INT7 pin of the DSP. After the DMA controller is done with
the whole block transfer, one interrupt is generated which terminates the DMA
and calls the callback function specified by the ths140x_rblock call.
3.3.6
Example Main Function
The following steps are necessary in order to use the example with DSP/BIOS:
Add the interrupt functions to the appropriate interrupt dispatch mecha-
nism. One way to do this is to use the DSP/BIOS:
Add a configuration database to the project or open an existing one.
Go to the HWI module and insert the following two functions:
_ths140x_risr
in
HWI_INT8,
DMA_Channel_0, Use Dispatcher = false
interrupt
source:
If DSP/BIOS is not used, the ISR must be included in the implemented interrupt
dispatch mechanism.
The example main function transfers a block of samples from the THS14xx to
the DSP memory.
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