IDEC MicroSmart - Manual (Page 149)

5: S PECIAL F UNCTIONS
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Using Partial Program Download
The partial program download function can download a maximum of 600 bytes (100 steps) of user program. When the
modified rungs of the user program exceed 600 bytes, the partial program download cannot be used. Make sure that modi-
fication is within 600 bytes.
When modifying two or more rungs of a user program, make sure that the difference between the first address and last
address of the modifications is within 600 bytes (100 steps).
While the partial program download is in progress, the scan time extends for several scans by approximately 200 ms per
scan.
While the partial program download is in progress, the statuses of outputs, internal relays, shift registers, timers, counters,
and data registers are unchanged.
When timer or counter preset values in the CPU RAM have been changed by using WindLDR (Online > Point Write), the
new preset values are cleared if the downloaded user program includes changes of the timer or counter instructions, and
the preset values of the downloaded user program take effect. Similarly, when a timer or counter is designated as a destina-
tion operand of an advanced instruction and the timer/counter preset value has been changed by the advanced instruction,
the new preset value is also cleared. However, if the downloaded user program does not include changes of timer or
counter instructions, the new preset values remain in effect.
If you do not want to clear the new preset values during the partial program download, you can import the new preset val-
ues to the user program. Access the PLC Status dialog box from the Online menu in the monitoring mode. Then click the
Confirm button in the TIM/CNT Change Status field. (The displayed status will switch from Changed to Unchanged.)
Upload the user program, which has new preset values in place of the original preset values. Make changes to the uploaded
user program, then perform the partial program download. Note that the Confirm button has effect on both timer and
counter preset values.
While the partial program download is in progress, interrupt inputs, timer interrupt, and catch inputs are disabled tempo-
rarily until the downloaded user program is loaded to the user program area (RAM) in the CPU module.
When changes are made to user communication instructions, pulse instructions, input filters, catch inputs, interrupt inputs,
timer interrupt, expansion data registers, high-speed counters, or Function Area Settings, download the entire user pro-
gram. If the partial program download includes these changes, the user program cannot run correctly.
When you want to delete a rung and perform the partial program download, use the disable rung command (Right Mouse
> Disable Rung) on
WindLDR instead. When a rung is deleted, the partial program download may not be performed
because each rung contains information to enable partial program download.
When a user program has been downloaded with comment data to the CPU module, the partial program download cannot
be performed. Make sure that the CPU module contains a user program downloaded without comment data to enable par-
tial program download.
Confirm Button After pressing the Confirm
button, the display
changes to “Unchanged.”