JYTEK NuDAQ PCI-69222, User Manual

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Operation Theory 61
X4 Encoder Mode
This mode is similar to X1 Encoder Mode, except that the
amount of counter value increases or decreases by four. Refer
to Figure 4-35.
Figure 4-35: X4 Encoder Mode
Phase Z
Each encoder mode may use a third phase, phase Z, that is
also frequently used for the index phase. You may decide if the
counter needs to be reloaded a specified value when phase Z
is at a logic high level with phase A and B at a specific logic
condition.
You must ensure that the logic level of phase Z is high during
at least a portion of the phase you specify for reload when you
use phase Z. Otherwise, the counter does not reload.
In Figure 4-36, the reload phase is when the logic level of phase A is
high, phase B is low, and phase Z is high in X1 Encoder Mode. In
addition, reloading takes higher priority than increment or
decrement of counter value. The reload occurs within one maximum
CLK period after the reload phase becomes true. After the counter
value is reloaded, the counter continues to count as before.