6F8C0845
15
1.5 Specifications of the DN611
1
(2) Instruction execution time in accessing the DN611 from the S controller
In sending output data to slave devices from the S controller via the DN611, the
output data is written in the DN611 from the S controller by an MWRITE instruction. In
sending input data from a slave device via the DN611, the input data is read from the
DN611 by an MREAD instruction. Table 1-6 lists the instruction execution times of
the S controller.
The DN611 has an output data area of 128 words (area where output data to slave
devices is stored) and an input data area of 128 words (area where input data from
slave devices is stored). Table 1-7 lists the execution times for WRITE/READ
instructions by the S controller in accessing 128 words. A WRITE/READ instruction is
capable of batch transfer of 128 words maximum only.
When input/output data with slave devices is smaller than 128 words, it takes less
time to execute an instruction. If the output data area or input data area is accessed
more than once, the time of executing instruction will be as much as the number of
accesses made to it.
(The output data area and input data area are explained in 4.2.1 Input/output data
areas.)
N: Number of words to transfer
I/O access time (MREAD) : 8.72
µ
s
I/O access time (MWRITE) : 8.32
µ
s
The values in Table 1-7 indicate the time required accessing the DN611. If two or more
DN611s are mounted, calculate the total time of executing instructions by adding the time
of access to each DN611.
If the total of the time lengths required for the S controller to access two or more DN611s
and for other than accessing the DN611s, that is, input/output and internal processing, is
greater than the response time of the system you require, a single S controller is
insufficient to cover the entire system. Mount the DN611s in separate S controllers
according to your system configuration.
Table 1-6 READ/WRITE Instruction Execution Time (
µ
s)
MREAD instruction
14.72 + (4 + N)
×
I/O access time
MWRITE instruction
14.48 + (4 + N)
×
I/O access time
Table 1-7 Maximum Execution Time for DN611 Access (ms)
(128 words for input/output)
MREAD instruction
1.17
MWRITE instruction
1.12
Total
2.29
