ALTUS Nexto Series User Manual

4. INITIAL PROGRAMMING
4. Initial Programming
The main goal of this chapter is to help the programming and configuration of Nexto Series CPUs, allowing the user to
take the first steps before starting to program the device.
Nexto Series CPU uses the standard IEC 61131-3 for language programming, which are: IL, ST, LD, SFC and FBD, and
besides these, an extra language, CFC. These languages can be separated in text and graphic. IL and ST are text languages
and are similar to Assembly and C, respectively. LD, SFC, FBD and CFC are graphic languages. LD uses the relay block
representation and it is similar to relay diagrams. SFC uses the sequence diagram representation, allowing an easy way to see
the event sequence. FBD and CFC use a group of function blocks, allowing a clear vision of the functions executed by each
action.
The programming is made through the MasterTool IEC XE (IDE) development interface. The MasterTool IEC XE allows
the use of the six languages in the same project, so the user can apply the best features offered by each language, resulting in
more efficient applications development, for easy documentation and future maintenance.
For further information regarding programming, see MasterTool IEC XE User Manual - MU299609, MasterTool IEC XE
Programming Manual - MP399609 or IEC 61131-3 standard.
4.1. Memory Organization and Access
Nexto Series uses an innovative memory organization and access feature called big-endian, where the most significant byte
is stored first and will always be the smallest address (e.g. %QB0 will always be more significant than %QB1, as in table
below, where, for CPUNEXTO string, the letter C is byte 0 and the letter O is the byte 7).
Besides this, the memory access must be done carefully as the variables with higher number of bits (WORD, DWORD,
LONG), use as index the most significant byte, in other words, the %QD4 will always have as most significant byte the %QB4.
Therefore it will not be necessary to make calculus to discover which DWORD correspond to defined bytes. The table below,
shows little and big endian organization.
MSB ← Little-endian → LSB
BYTE %QB7 %QB6 %QB5 %QB4 %QB3 %QB2 %QB1 %QB0
C P U N E X T O
WORD %QW3 %QW2 %QW1 %QW0
CP UN EX TO
DWORD %QD1 %QD0
CPUN EXTO
LWORD %QL0
CPUNEXTO
MSB ← Big-endian → LSB
BYTE %QB0 %QB1 %QB2 %QB3 %QB4 %QB5 %QB6 %QB7
C P U N E X T O
WORD %QW0 %QW2 %QW4 %QW6
CP UN EX TO
DWORD %QD0 %QD4
CPUN EXTO
LWORD %QL0
CPUNEXTO
Table 31: Memory Organization and Access Example
32

ALTUS Nexto Series Specifications

General

Brand	ALTUS
Model	Nexto Series
Category	Computer Hardware
Language	English