After the thresholds are programmed, set the access control bit to “1” by writing a byte of 01H into the auxiliary control register. This will make the following read/write operation access the data bytes in the FIFO instead of it’s thresholds. It is recommended that the access control bit be set to “1” when sending other commands (flush scan list, stop A/D, or trig/arm) to the DAQP card by writing into the auxiliary control register. A useful tip for safe operation is to set the bit to “0” only when flushing and programming the FIFO thresholds. Although the almost empty threshold is never used, it must be programmed because the four configuration bytes must be accessed as an entire entity.
5.2.6.6 Latch Timer/Counter Command
This command will latch the current value of the timer/counter into the 16 bit read latch register and can be executed if the timer/counter is running (on the fly) or not. The latched value will not change until a new latch command is issued again.
5.2.7 D/A Data Port (base + 8, base + 9)
The D/A data port can be accessed either as a
Bit 12 to 15 selects the D/A channel, in which bit 13, 14 and 15 must all be set to “0”, while bit 12 is “0” for selecting D/A channel 0 or “1” for D/A channel 1.
Table 5-18. D/A Data Port Bit Definition
| Bits |
| Definition |
| Explanation |
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| Reserved |
| all “0” |
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| 12 |
| D/A channel selection |
| “0” for channel 0, “1” for channel 1 |
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| D/A output code value |
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5.2.7.1 D/A Channel Output
Bits 0 to 11 specify the D/A channel data, which is always in 2’s complement format. The bipolar D/A channel output ranges from
U = (C*5/2048)
The output of D/A channel 1 is used for setting the analog trigger threshold.
53 |