Siemens SIMATIC NET SPC 4-2 LF Manual page 60

Byte 0: Control Command
Bit Meaning
0 Reserved
1 Clear_Data
2 Unfreeze
3 Freeze
4 Unsync
5 Sync
6,7 Reserved
Table 6-2 : Global Control
60
"Reserved" indicates that these bits are reserved for future expansions and
must have the value "logical 0".
If the bit "Check-GCT-Resbits-Off = 0" is set in mode register 2, the reserved
bits are scanned for zero. If at least one of the reserved bits has the value
"logical 1", the SPC 4-2 executes "Leave-Master".
If "Check-GCT-Resbits-Off = 1" is set, the reserved bits for the SPC 4-2 are
"don't care".
Output data in the indication buffer are deleted and the
Output_Data_Exchange interrupt is generated.
If unfreeze is set, the SPC 4-2 deactivates the freeze mode (DIAG.FREEZE
mode = 0) and swaps the reply update buffers D and N if the flag RUP-N-
Valid = 1 is set in the DEFAULT SAP. The SPC 4-2 then sets RUP-N-Valid =
0. These actions are executed with lock active.
If "DIAG.FREEZE-Mode = 0" is set, the SPC 4-2 replies to a request frame
requesting input data with the "new" input data (in other words, the SPC 4-2
swaps the reply update buffers D and N prior to sending the response if the
flag RUP-N-Valid = 1 is set in the DEFAULT SAP).
If freeze is set, the SPC 4-2 activates the freeze mode (DIAG.FREEZE mode
= 1) and swaps the reply update buffers D and N if the flag RUP-N-Valid = 1
is set in the DEFAULT SAP. The SPC 4-2 then sets RUP-N-Valid = 0. The
SPC 4-2 executes these actions with lock active. If input data are requested
from the SPC 4-2 with a request frame in the freeze mode, the SPC 4-2
responds with the "old" input data of reply update buffer D (in other words,
reply update buffers D and N are not swapped prior to sending the response.
If unsync is set, the SPC 4-2 deactivates the sync mode (DIAG.SYNC mode =
0) and swaps the indication buffers D and N if valid data are entered in the D
buffer. It also sets the IND-N-Valid = 1 flag in the DEFAULT SAP and
generates the "Output-Data-Exchange" interrupt.
If DIAG. SYNC mode = 0 is set when a global control frame with unsync = 1 is
received, unsync has no effect.
If DIAG.SYNC mode = 0, the SPC 4-2 swaps the indication buffers D and N
immediately when it receives new valid output data.
If sync is set, the SPC 4-2 activates the sync mode (DIAG.SYNC mode = 1),
without swapping the indication buffers D and N. If DIAG.SYNC mode = 1 is
set when a global control frame with sync = 1 is received, the SPC 4-2 swaps
the indication buffers D and N if the D buffer contains valid output data. It also
sets the IND-N-Valid = 1 flag in the DEFAULT SAP and generates the
"Output-Data-Exchange" interrupt. The SPC 4-2 executes these actions with
lock active.
If DIAG.SYNC mode = 1 is set, the SPC 4-2 enters new output data from the
DP master in indication buffer D and generates the "Watchdog-Reset"
interrupt. The SPC 4-2, however, waits until the next "Sync" command before
swapping the indication buffers D and N.
see bit 0
Meaning
PROFIBUS Controller SPC 4®-2 LF
C79000-G8976-C157-3