
1.PROFIBUS-DP MASTER FUNCTIONS SETTING B-63994EN/02
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Data concurrency
When a ladder program uses DI data or DO data in long data (4-byte
data) units and in word data (2-byte data) units, concurrency of
multiple bytes of data (with no data split) is guaranteed under the
restrictions explained below.
CAUTION
If the restrictions described in this section are not
observed, concurrency of long data and word data
cannot be guaranteed.
Concurrency of long data (4-byte data)
To ensure data concurrency, the following two conditions must be
observed:
(1) In the ladder program, the following instructions must be used in
units of four bytes:
DECB, CODEB, DCNVB, COMPB, DSCHB, XMOVB, ADDB,
SUBB, MULB, NUMEB, MOVN, EOR, AND, OR, and NOT
instructions
(2) When DI data or DO data is assigned to PMC R or E addresses,
R or E addresses must be on 4-byte boundaries.
Example) 1:R0000, 2:R0004, 3:R0008, 1:E0000
Concurrency of word data (2-byte data)
To ensure data concurrency, the following two conditions must be
observed:
(1) In the ladder program, the following instructions must be used in
units of two bytes:
DECB, CODEB, DCNVB, COMPB, DSCHB, XMOVB, ADDB,
SUBB, MULB, NUMEB, MOVN, EOR, AND, OR, and NOT
instructions
(2) When DI data or DO data is assigned to PMC R or E addresses,
these addresses must be on 2-byte boundaries.
Example) 1:R0000, 2:R0002, 3:R0004, 1:E0002
Concurrency of byte data (1-byte data)
There is no special restriction. Within 1-byte data, concurrency is
always ensured.