Data Translation DT9834 Series, Руководство пользователя

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Principles of Operation
81
Note: To read the entire 32-bit value, specify the channel corresponding to the lower 16-bit
word first, followed by the channel corresponding to the upper 16-bit word.
While you can read the lower 16-bit word of a 32-bit counter, you cannot read just the upper
16-bit word.
The counter/timer channel is treated like any other channel in the analog input channel list;
therefore, all the clocking, triggering, and conversion modes supported for analog input
channels are supported for the counter/timers, if you specify them this way.
Maximum Rate
The maximum rate at which the module can read the counter/timers depends on the total
number of counter/timer channels and analog input channels (see
page 79 ) in the list and
whether or not you are reading the digital input port (see page 80 ). Remember that each 32-bit
counter requires two channels in the channel list.
For example, since the maximum throughput of the analog input subsystem is 500
kSamples/s, the module can read one analog input channel and one counter/timer (three
channels total) at a maximum sample rate per channel of 166.667 kSamples/s. To read three
analog input channels and one counter/timer (five channels total), the maximum sample rate
per channel is 100 kSamples/s.
Table 8: Using Counter/Timers in Analog Input Channel List
Counter/Timer
Channel Description
Channel to Specify in Channel
List for:
Modules with
16 SE or 8 DI
Channels
Modules with
32 SE or 16 DI
Channels
C/T_0_LOW Lower 16 bits (0 to 15) of C/T 0 Channel 17 Channel 33
C/T_0_HI Upper 16 bits (16 to 31) of C/T 0 Channel 18 Channel 34
C/T_1_LOW Lower 16 bits (0 to 15) of C/T 1 Channel 19 Channel 35
C/T_1_HI Upper 16 bits (16 to 31) of C/T 1 Channel 20 Channel 36
C/T_2_LOW Lower 16 bits (0 to 15) of C/T 2 Channel 21 Channel 37
C/T_2_HI Upper 16 bits (16 to 31) of C/T 2 Channel 22 Channel 38
C/T_3_LOW Lower 16 bits (0 to 15) of C/T 3 Channel 23 Channel 39
C/T_3_HI Upper 16 bits (16 to 31) of C/T 3 Channel 24 Channel 40
C/T_4_LOW Lower 16 bits (0 to 15) of C/T 4 Channel 25 Channel 41
C/T_4_HI Upper 16 bits (16 to 31) of C/T 4 Channel 26 Channel 42