Toshiba T2N - Manual (Page 122)

2.INTERNAL OPERATIONS
User’s manual 109
If we consider the T2N operation simply from the viewpoint of external signal
exchange, batch I/O processing and user program execution can be considered
to be repeated continuously, as shown in the following diagram.
latest input data incorporated in XW
YW data output externally
batch I/O processing
running user program
scan
YW data fixed with reference to XW data
So basically, this has the advantage that high speed scans can take place so
that I/O module data is not exchanged during user program execution and also
it is easy to create program logic which prevents XW data changing during user
program execution. This method is called the batch I/O processing method
(refresh method).
There is also another method of the T2N operation whereby I/O module data
exchange takes place during user program execution, using IW/I instead of
XW/X and OW/O instead of YW/Y. This method is called the direct I/O processing
method. It is recommended that the I/O modules used in direct I/O are inhibited
the batch I/O (they have i specification on I/O allocation) so shorten the time for
batch I/O processing.
1. Use the following criteria for batch I/O processing time.
2. input (XW)
3. output (YW)
4. link(W) ... 8 µs/register
5. (LW) ... 22µs/register
6. I/O modules with i specification on I/O allocation (iX, iY, iX + Y) are not
part of batch I/O processing. Refer to Part 3 for I/O allocation.
7. Forced input device (X), link register relay (Z), and link relay (L) are not part
of batch I/O processing. The force function is explained in section 5.
8. Refer to the data transmission module manual for the allocation of the link
register/relay (W/Z and L/LW) to the data transmission module.
9. With the direct I/O processing method, output is in register units even
when the bit (O) is specified. Refer to Part 3 for direct I/O registers.
... approximately 45µs/register
NOTE