Omron DEVICENET#05-2003 - Page 201

192
Remote I/O Communications Characteristics Section 6-1
• For details about the communications time required for 1 Slave refer to
page 192. For the MULTIPLE I/O TERMINAL, it equals the communica-
tions time required for 1 Slave Unit of the Communications Unit.
Σ (com-
munications time per Slave) is the total of the communications times for all
the Slaves in the network.
• Multiple Units processing time = 3.5 (ms). It is to be added only if there is
a Slave where the input or output exceeds 8 bytes.
• Explicit message processing time = 0.11
× T
B
+ 0.6 (ms). It is to be added
only when explicit message communications are executed. T
B
is a fixed
value (At 500 kbps = 2, 125 kbps = 4, 125 kbps = 8).
• N = Number of Slaves
Communications Time per
Slave
The communications time per Slave is the communications time required for a
single Slave. The formula for calculating the communications time per Slave
(T
RT
) for different types of Slave is shown below. For the MULTIPLE I/O TER-
MINAL, it will be the communications time per Slave of the Communications
Unit. With the MULTIPLE I/O TERMINAL, 2 input words (4 bytes) are used for
notifying the status of I/O Unit interfaces. This must be included as the num-
ber of bytes when making calculations.
Output Slave with 8 Bytes of Output or Less
T
RT
= 0.016 × T
B
× S
OUT1
+ 0.11 × T
B
+ 0.07 (ms)
S
OUT1
:Number of output words for the Output Slave
T
B
: At 500 kbps = 2, 250 kbps = 4, 125 kbps = 8
Input Slave with 8 Bytes of Input or Less
T
RT
= 0.016 × T
B
× S
IN1
+ 0.06 × T
B
+ 0.05 (ms)
S
IN1
: Number of input words for the Input Slave
T
B
: At 500 kbps = 2, 250 kbps = 4, 125 kbps = 8
Mixed I/O Slave with 8 Bytes of Both Input and Output or Less
T
RT
= 0.016 × T
B
× (S
OUT2
+ S
IN2
) + 0.11 × T
B
+ 0.07 (ms)
S
OUT2
:Number of output words for the Mixed I/O Slave
S
IN2
: Number of input words for the Mixed I/O Slave
T
B
: At 500 kbps = 2, 250 kbps = 4, 125 kbps = 8
Slave with more than 8 Bytes of Input or Output (or Both)
T
RT
= T
OH
+ T
BYTE-IN
× B
IN
+ T
BYTE-OUT
× B
OUT
(ms)
T
OH
: Protocol overhead
T
BYTE-IN
: Input byte transmission time
B
IN
: Number of input bytes
T
BYTE-OUT
: Output byte transmission time
B
OUT
: Number of output bytes
If there are no Output Slaves, use 0 as the value of B
OUT
. If there are no input
Slaves, use 0 as the value of B
IN
.
Communication speed T
CH
T
BYTE-IN
T
BYTE-OUT
500 kbps 0.306 ms 0.040 ms 0.036 ms
250 kbps 0.542 ms 0.073 ms 0.069 ms
125 kbps 1.014 ms 0.139 ms 0.135 ms