Siemens Sinumerik 840DiE sl - Page 502

01/2007
18.2 Expanded message frame configuration/evaluation of internal drive variables
18-502
© Siemens AG 2007 All Rights Reserved
SINUMERIK 840Di sl Manual (HBIsl) – 01/2007 Edition
Note
S The message frame configuration must meet the following condition:
(Standard PDA + Additional PDA) – 1  n
where n = maximum possible index for system variable $VA_DP_ACT_TEL
S When using the system variables $VA_DP_ACT_TEL[n, a] in a user
program, it is only permissible to use one constant as index n.
Application example for system variables in a synchronized action:
IDS=1 DO $AC_MARKER[0] = $VA_DP_ACT_TEL[12, X]
The user must take the following points into account with regard to the data for-
mats of the process data stored in the system variables:
S The process data are transferred in the message frame in the following format:
– unsigned 16–bit integer (UINT16)
are transferred. They are stored in the system variables in the format
– signed 32–bit integer (INT32)
In the necessary format conversion, bit 15 of the unsigned 16–bit integer
PDA value is transferred to bits 16 to 31 of the signed 32–bit integer value in
the system variable. For the physical unit as well as the drive–end weighting
of the drive actual values transferred in the additional PDA, please refer to
the data description of the specific drive documentation.
S Drive actual values composed of 2 PDAs (both 16–bit) e.g.
– Encoder 2 position actual value 1 (G2_XACT1)
– Encoder 2 position actual value 2 (G2_XACT2)
are mapped on two separate data words (both 32–bit) in the system variable
$VA_DP_ACT_TEL.
Fig. 18-2 shows how the process data of the message frame are mapped onto
system variable $VA_DP_ACT_TEL:
PDA: Standard
message frame
PDA1 . . . . . PDAx+1PDAx PDAy. . . . .
PDA: Additional
drive data
PDA for expanded message frame
System variable $VA_DP_ACT_TEL[n, a]
PDA1 . . . . . PDAx+1PDAx PDAy. . . . .
0
31
15 015015 015
0
Index n = 0 Index n = x Index n = yIndex n = x+1
1516 31 0
1516
31 0
1516
31 0
1516
Bit 31...16 = bit
15
Bit 31...16 = bit
15
Bit 31...16 = bit
15
Bit 31...16 = bit
15
Fig. 18-2 Mapping principle: PDA on system variable $VA_DP_ACT_TEL
Data formats
18 840Di–s
p
ecific Data and Functions