98
FX
3U
/FX
3UC
Series Programmable Controllers
Programming Manual - Basic & Applied Instruction Edition
4 Devices in Detail
4.7 High Speed Counter [C]
4.7.9
Condition handled as software counters
High speed counters are classified into hardware counters and software counters. In some conditions,
however, hardware counters are handled as software counters.
In this case, use hardware counters within the range of maximum response frequency and total frequency
determined for software counters.
Condition handled as software counters
Counter No.
Condition in which hardware counters are handled as software counters
C235
C236
C237
C238
C239
C240
C244(OP)
C245(OP)
C246
C248(OP)
C251
C253(OP)
Because hardware counters execute counting at the hardware of the FX
3UC
, they can execute counting
without regard to the total frequency. However, hardware counters are handled as software counters
when used in the following condition. In this case, their maximum response frequency and total
frequency are limited in the same way as other software counters. Use M8380 to M8387 to check
whether high speed counters are handled as hardware counters or software counters.
•
When DHSCS (FNC 53), DHSCR (FNC 54), DSHZ (FNC 55) or DHSZ (FNC280) instruction is used
for a hardware counter number, the hardware counter is handled as a software counter.
Example: C235
In this case, C235 is handled as a software counter.
•
When an index register is used for a counter number specified in DHSCS (FNC 53), DHSCR
(FNC 54), DHSZ (FNC 55) or DHSCT (FNC280) instruction, all hardware counters are handled as
software counters.
Example: C235Z0
•
The counter C253 is handled as a software counter when the logic of the external reset input signal is
inverted.
Example: When the logic of the external reset input signal for the software counter C241 is inverted
→
For logic inversion of the external reset input signal, refer to Subsection 4.7.6.
DHSCS
K100
C235
Y000
C235
K
{{{
DHSCS
K100
C235Z0
Y000
M8388
M8389
C241
K
{{{
