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MELSEC-Q
5 BASIC USAGE
(a) The ring counter will operate as follows when the "present value < ring
counter minimum value" or "ring counter maximum value < present value".
• For up count
Even if the present value reaches the ring counter minimum value, the
ring counter minimum value will be retained as is. With the next addition
pulse, (ring counter maximum value +1) will be stored as the present
value.
• For down count
When the present value reaches the ring counter maximum value, the ring
counter minimum value is automatically stored as the present value.
In counting up and down, the ring counter upper limit value is not stored in
CH
Present value (Un\G2, Un\G3, Un\G34, Un\G35).
For example, if the count is enabled with the ring counter minimum value of
0, the ring counter maximum value of 2000 and the present value of 3000,
the count range and present value will change as shown in the figure below.
-2147483648
Ring counter minimum value
Present value
Ring counter maximum value
0
3000
2000
2147483647
Ring counter
minimum value
Ring counter
maximum value
(2000)
Present value
3000 3001 2001to -2 -1 0 to2002 2998
2147483647 -2147483648
to 2999
Counting range
Counting range
Ring counter maximum value, 2000
is not stored in CH Present value
(Un\G2, Un\G3, Un\G34, Un\G35).
(b) When "Ring counter lower limit = Ring counter upper limit" is met, a value
that can be expressed in 32-bit signed binary (-2147483648 to 2147483647)
will be the counting range, regardless or the present value.
POINT
(1) While CH Count enable command (Y4, YC) is on, even if values are written
to CH
Ring counter minimum value (Un\G20, Un\G21, Un\G52, Un\G53) and
CH
Ring counter maximum value (Un\G22, Un\G23, Un\G54, Un\G55), the
stored values do not change.
Turn off CH
Count enable command (Y4, YC) before changing the ring
counter upper/lower limit value.
(2) Turn off CH
Count enable command (Y4, YC) before changing the count
range by the preset function.