Select Register; Selectregister - Siemens SIMATIC S5 IP 281 Equipment Manual

Software Setfinw

Select Register

3.2
A register set is selected to address the registers for the 1P 281. The allocation of the registers to
the ;ets is shown in the following figure.
Reg. Set O
Offset O
1
2
3
Write
4
Parameter
register 1
5
6
Parameter
register 2
7
Offset O
1
2
Status reg. 1
3
Status reg. 2 I
Read
Status reg. 3 I
4
5
6
7
When a counter is operated in 16–bit mode, only byte O and byte 1 are used when 4–byte re–
incremented by 2).
A register set is selected in the select register. The register set remains selected until a new value
is entered in the select register.
The ERROR LED goes on for all other entries. The select register is always addressed with offset
address O regardhss of the register set selected. The selec~ register can-not be read back.
Caution
When a set is selected in the interrupt program (e.g., to read out the IIR), this call
causes the current set selection in the cyclic program to be lost. This makes it
necessary to save the selected set for all read and write procedures for which the
interrupts are not disabled IA/RA). The selected set address must then be saved in
a selected memory location and reloaded at the end of the interrupt program.
3 – 4
-
Reg. Set 1 Reg. Set 2
Select reg.
—
—
—
Load
Interrupt
register 1 register 1
Counter
value
register 1
Counter
value
register 2
Register Set Contents of the Select
Register
o
OH
1 IH
2 2H
3 3H
I
4
4H
R 11/92
Reg. Set 3 Reg. Set 4
Select reg. Select reg.
- — — — — -
—
- — — — — -
—
—
IFR 2
Load Interrupt
register 2 register 2
I