Chapter 5
Programming
© National Instruments Corporation
5-23
AT-MIO-64F-5 User Manual
In this mode, Counter 1 counts the programmed number of cycles before terminating the
sequence. Counter 2 then begins counting the time between cycles, the cycle interval, then
restarts the sequence. This sequence of events continues ad infinitum and does not stop until the
update signal is removed or the DAC circuitry is cleared.
This sequence requires that the GATE2SEL signal in addition to the SRC3SEL signal be set in
Command Register 4. This allows Counter 1 to count the buffer retransmit signals from the
source line of Counter 3 while Counter 2 is gated by the signal at its own gate pin.
Waveform Generation Programming Functions
This section provides a detailed explanation of the programming functions necessary to generate
synchronously timed analog output waveforms.
Clearing the Analog Output Circuitry
This involves clearing the TMRREQ, DACCOMP, and DMATCA or DMATCB bits in the
Status Register. To do this, access the TMRREQ Clear, DAC Clear, and if necessary, the
DMATCA or DMATCB Clear registers.
Selecting the Internal Update Counter
Select the desired signal at the RTSI switch to be used for updating the DACs. OUT1, OUT2,
OUT3 (available as EXTCONV*), and OUT5 are available for updating. To route these update
signals, the A side pin of the RTSI switch must be internally routed to the B side, or trigger side.
Select a trigger line that is not being used. The signal must be routed from the selected B side
trigger line to the A4 pin on the RTSI switch. All of this is done in one programming sequence
by shifting a 56-bit value to the RTSI switch. See the
RTSI Bus Trigger Line Programming
Considerations
section later in this chapter.
Notice that if OUT5 is to be used for updating, it does not need to be routed across the RTSI
switch. In this case only is it sufficient to enable A4DRV to drive pin A4 of the RTSI switch
with OUT5.
Programming the Update-Interval Counter
Select the appropriate counter (1, 2, 3, or 5) from the Am9513A Counter/Timer to be used for
updating the DACs. Active low pulsing and no gating should be part of the mode programmed.
To program the update-interval counter, complete the following programming sequence. All
writes are 16-bit operations. All values given are hexadecimal.
1. Write FF00 +
n
to the Am9513A Command Register to select the Counter
n
Mode Register.
2. Write the mode value to the Am9513A Data Register to store the Counter
n
mode value.
Am9513A counter mode information can be found in Appendix E,
AMD Am9513A Data
Sheet
. Use one of the following mode values:
0225
Ð Selects 5 MHz clock (from SOURCE2 pin)
0B25 Ð Selects 1 MHz clock
0C25 Ð Selects 100 kHz clock
0D25 Ð Selects 10 kHz clock
Содержание AT-MIO-64F-5
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