Allen-Bradley 1779-KFMR User Manual page 129

Program scan is inhibited.
Programming terminal access is inhibited.
A PLC-2/05, PLC-2/15, PLC-2/16, PLC-2/17, or PLC-2/30 processor is
put into the program-load mode. With the last-state switch at each I/O
chassis set to OFF, the outputs turn off. The outputs of a PLC-2/20 or
Mini-PLC-2 processor remain enabled if the mode-select switch is in
the RUN or RUN/PROG position.
WARNING: Leaving outputs on during a download could
cause unexpected machine motion. If you send an enter
download mode command to a PLC-2/20 or Mini-PLC-2 station
with the mode-select switch in the RUN or RUN/PROG
position, the only way to turn off all outputs is to immediately
send a physical write command to set all output image bits to 0.
The PLC-2 station will not send any commands.
The PLC-2 station does not accept any commands except set data table
size, mode-setting, physical read, physical write, or diagnostic
commands.
Upload
To ensure a stable program image during an upload, the 1779-KP2
interface must prohibit program changes during an upload. The interface
will block other access to the PLC-2 memory during upload if the general
uploading procedure follows this order:
Enter Upload Mode
Physical Read
.
.
.
Physical Read
Exit Download/Upload Mode
For the enter upload mode command to be accepted by an interface for a
PLC-2/05, PLC-2/15, PLC-2/16, PLC-2/17, or PLC-2/30 processor, the
mode-select switch must be in the RUN/PROG or PROG position. The
mode-select switch of a PLC-2/20 or Mini-PLC-2 processor can be in any
position. The results of the enter upload mode command are:
Programming terminal access is disabled.
The PLC-2 station does not accept any commands except mode-setting
or physical read commands.
Chapter 8