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64
DMx820 User’s Manual
•
Count value writing during counting: The new count value is written to the CE at the falling edge of the next clock pulse, and counting
continues using the new count value. The operation for 2-byte count is as follows:
o
First byte writing does not affect the counting operation.
o
After the second byte is written, the new count value is loaded to the CE at the falling edge of the next clock pulse.
•
This means that the counting operation is retriggered by software. The output strobe is set to “L” level upon input of N+1 cl
ock pulses
after the new count value N is written.
Mode 5
•
Application: Hardware trigger strobe
•
Output operation: The output is initially set to “H” level. When the counter value becomes 0 after triggering by the rising
edge of the gate
pulse, the output goes to “L” level during one clock pulse, and then restores “H” l
evel.
•
Count value load timing: Even after the control word and initial count value are written, loading to the CE does not occur until the input
of the clock pulse succeeding the trigger. For the clock pulse for CE loading, the count value is not decremented. If the initial count value
is N, therefore, the output is not set to “L” level until N+1 clock pulses are input after triggering.
•
Gate function: The initial count value is loaded to the CE at the falling edge of the clock pulse succeeding gate triggering. The count
sequence can be retriggered. The gate pulse does not affect the output.
•
Count value writing during counting: The count value writing does not affect the current counting sequence. If the gate trigger is generated
after the new count value is written and before the current counting ends, the new count value is loaded to the CE at the falling edge of
the next clock pulse, and counting continues using the new count value. The various roles of the gate input signals in the above modes
are summarized in the following table.