Yaskawa Modicon 800 Series Remote I/O Network for use on Microtrac LAN - Manual (Page 17)

3 SOFTWARE
16 PLC Programming for GETN & RDCI PAC Blocks
5/24/96
• PLC In Item — the choice of one of the eight registers being used on the
input register card. In this case register one is being used.
• PLC Out Chan — the simulated output register card location on the
Modicon network. Number designate the drop and slot for that 8 channel
output register card (B864). In this case simulated card is in drop 2, slot 2,
and always rack 2.
• PLC Out Item — the choice of one of the eight registers being used on
the output register card. In this case register one is being used.
• FCTN — the function number being used.
• DP — the decimal point.
The PLC gateway provides transfers of both logical and numeric data between
the drive and the PLC. When the PLC gateway detects a change in data from
the PLC, the drive which initialized that parameter will be updated with the
new data. The data transition initiates this exchange. This new value is
returned to the PLC as confirmation of a successful update. When this
parameter is changed from the keypad, the gateway updates the PLC with the
new value and expects the new value to be returned as confirmation of the
exchange.
Power-up
Power-up represents a special condition. There are two locations of non-
volatile memory for the same parameter, the drive and the PLC. The drive
memory is chosen as the default on a power-up condition. To insure proper
initialization of the RDCI and GETN blocks during power-up, the PLC
gateway will inhibit transfers from the PLC until the drive data confirmation is
returned from the PLC on power-up.
A sample ladder diagram is shown. It illustrates the technique used to satisfy
the requirements. The first rung moves data from the PLC into the write
register. The second rung is conditional upon a change in the read data from
the last PLC scan and will move data from the read transfer register into the
write transfer register. The third rung executes the write to the PLC gateway
register. The fourth rung moves the latest data from the drive into a register
for the transition detector of rung 2.
RD 3004-20