Siemens SIMATIC NET SPC 4-2 LF Manual page 75

Bit 0 XHOLDTOKEN
Here, the level of the output pin XHOLDTOKEN can be set. This output exists only to ensure pin
compatibility with SPC2.
0 = Low
1 = High (reset value)
Bit 1 XINTCI
Here, the level of the output pin XINTCI can be set. This output exists only to ensure pin compatibility with
SPC2.
0 = Low
1 = High (reset value)
Bit 2 X86
This bit only influences the asynchronous Intel mode
0 = If this bit is cleared, access is started with the falling edge of ALE and access is therefore only
possible when ALE = 0. This allows an extremely fast series of accesses, for example for
1 = Following a reset, it has value 1 and disables the ALE input (in other words the level at this pin is
immaterial). The SPC 4-2 is therefore in the X86 mode and access is started by edges at
XRD/XWR.
Bit 3 Check-GCT-Length-Off
Check the frame length of a global control frame
0 = The length of a global control frame is monitored, if this is not 2, the GCT is ignored
1 = No monitoring of the data length
Bit 4 Check-GCT-Resbits Off
Check the reserved bits of a global control frame
0 = The reserved bits in the command byte of a global control frame are monitored.
1 = No monitoring of the reserved bits in the command byte of a global control frame. If at least one
of these reserved bits is logical 1, the SPC 4-2 executes a "Leave-Master".
Bit 5 SPEC-CLEAR-MODE
In the Spec_Clear_Mode (fail-safe mode), the SPC 4-2 accepts data frames with a net data length of 0
when the PROFIBUS master is in the clear mode.
0 = Fail-safe mode off
1 = Fail-safe mode enabled
Bit 6 EN-CLOCK-SYNC (time-of-day synchronization)
XPB/PA = 0 (PROFIBUS mode):
0 = No time-of-day synchronization (status following reset); in other words, SM2-Time0/1 frames are
filtered
1 = Time-of-day synchronization is active for several time masters
XPB/PA = 1 (PA mode):
0 = Time-of-day synchronization of the SPC 4 is set.
1 = Time-of-day synchronization is active for several time masters
Bit 7 EN-DDB-MODE
XPB/PA = 0 (PROFIBUS mode):
0 = All DDB frames are filtered (status following reset).
1 = DDB is enabled
XPB/PA = 1 (PA mode):
Status of EN-DDB-MODE unimportant, DDB mode is always enabled.
Table 7-14 :
The extension of mode register 2 in the SPC 4-1 and SPC4-2 is compatible with
the SPC 4 in terms of software since the current server software sets bits 5 to 7 of
the data bus to 0 when it makes the parameter settings in this register.
PROFIBUS Controller SPC 4®-2 LF
C79000-G8976-C157-3
80C165
Mode Register 2
ASIC Interface
75