Omron C200HE User Manual

Here, we’ll compute the cycle time for a simple PC. The CPU Unit controls only
I/O Units, eight on the CPU Rack and five on a 5-slot Expansion I/O Rack. The
PC configuration for this would be as shown below. It is assumed that the pro-
gram contains 5,000 instructions requiring an average of 0.156 

µ

s each to

execute.

CPU Rack

Expansion I/O Rack

12-point Output Units

8-point Output Unit

16-point Input Units

8-point Input Units

8-point Output Units

The equation for the cycle time from above is as follows:

Cycle time = 

Overseeing time + Program execution time + I/O refresh time +
Peripheral device servicing time

Overseeing

Fixed

0.7 ms

0.7 ms

Program execution

0.156 

µ

s/instruction

×

 5,000 instructions

0.78 ms

0.78 ms

I/O refresh

See below.

0.34 ms

0.34 ms

Peripheral device
servicing

Minimum time

0.26 ms

0.0 ms

The I/O refresh time would be as follows for two16-point Input Units, four 8-point
Input Units, two 12-point Output Units (12-point Units are treated as 16-point
Units), and five 8-point Output Units controlled by the PC:

8 pts

(16 pts 

×

 2) + (8 pts 

×

 4)

×

 20 

µ

s = 0.34 ms

×

 20 

µ

s +

8 pts

(16 pts 

×

 2) + (8 pts 

×

 5)

Here, the cycle time is computed for a PC with a Host Link Unit and Remote I/O
Master Unit installed. The PC configuration for this could be as shown below.

The CPU Unit controls three 8-point Input Units, three 8-point Output Units, a
Host Link Unit, and a Remote I/O Master Unit connected to a Remote I/O Slave
Rack containing four 16-point Input Units and four 12-point Output Units.