5 - 6                         5 - 6 
MELSEC-Q
5   DETAILS AND SETTING OF FUNCTIONS 
 
• Overflow error 
An overflow error (error code: 100) occurs if the "accumulating count value" of 
the buffer memory exceeds 99999999 when the count type is the linear counter. 
If the overflow error occurs, count operation is stopped, and the "accumulating 
count value" of the buffer memory does not change from 99999999 if pulses are 
input. Also, the "sampling pulse number" of the buffer memory is reset. 
 
The overflow error is cleared by setting "1" in the "counter reset request" of the 
buffer memory. Count operation is resumed after the error is cleared. The error is 
also cleared by turning ON the error reset request (Y8 to YF). To resume count 
operation, however, turn ON the operating condition setting request flag (Y1) or 
set "1" in the "counter reset request" of the buffer memory. 
 
When checking for the module error at occurrence of an overflow error, click the 
[Diagnosis] - [System monitor] menu on GX Developer and monitor the system. 
 
Buffer memory address 
Item  Read value/Setting value 
CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 
Accumulating count value  0 to 99999999 
8 
9 
40 
41 
72 
73 
104 
105 
136 
137 
168 
169 
200 
201 
232 
233 
Overflow detection flag 
0: No overflow detection (OFF)
1: Overflow detection (ON) 
12 44 76 108 140 172 204 236 
Counter reset request 
1: Reset request 
(The value automatically 
turns to "0" after completion 
of a counter reset.) 
13 45 77 109 141 173 205 237