Chapter 4
Programming
©
National Instruments Corporation
4-53
The functions
MSC_IRQ_Configure
and
MSC_Pass_Through_
Polarity
allows you to select one of the IRQ 0-7 lines for Group A and
one for Group B and allows the enabling of pass-through interrupts
respectively. The Interrupt Control section also describes two interrupt
programs, one for Group A and one for Group B, which are skeletons of the
actual interrupt service routines. These programs do not address the
programming of the interrupt controller.
DMA Programming
You can program your AT E Series board so that the analog input, analog
output, or general purpose counter/timers can generate DMA requests
under appropriate circumstances. There are three logical DMA
channels—A, B, and C. There are three registers—Channel A Mode
Register (address 0x03), Channel B Mode Register (address 0x05), and
Channel C Mode Register (address 0x07)—corresponding to these logical
channels. These registers have bits to enable the logical channels, enable
interrupts on terminal count, define the transfer type and finally define
which physical DMA channel is associated with the logical channel.
Each logical channel, in turn, can service either analog input, analog
output, or the general-purpose counter/timers. You must program the AO
AI Select Register (address 0x09) and the G0GI Select Register (address
0x0B) to assign particular logical channels to either AI, AO, or GPCTs.
Figure 4-2 shows the three-stage DMA structure.
Figure 4-2. DMA Structure
Analog
Input
Analog
Output
GPCT1
GPCT2
Logical Channel Assignment
Logical
DMA
Channel A
Logical
DMA
Channel B
Logical
DMA
Channel C
Physical
DMA
Channel
Assignment
0
1
2
3
5
6
7
Содержание AT-AI-16XE-10
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