TC1796
Peripheral Units (Vol. 2 of 2)
Controller Area Network (MultiCAN) Controller
User’s Manual
22-118
V2.0, 2007-07
MultiCAN, V2.0
22.5.6
Local Offset and Global Time
On TTCAN level 2, the local offset of a TTCAN node (not of the time master) is defined
as the difference between the Master_Ref_Mark (also named Global_Ref_Mark) and the
node’s reference mark Ref_Mark. For the time master, the sum of the local time and the
local offset is stored as Global_Sync_Mark when the frame synchronization is reached.
The Global_Sync_Mark (for the time master) and the Global_Ref_Mark (for all other
nodes) are stored in the Global Mark Register GMR. The Local_Offset is stored in the
local offset register LOR.
When a TTCAN node receives a reference message, the global mark register is updated
by the received value. The value that has been received in the previous reference
message is automatically transferred from the global mark register to the last global mark
register. The difference between these two values represents the time elapsed between
the last two reference messages from the time master’s point of view.
Figure 22-27 Local Offset and Global Time
MCA05853
Reference
Message
Correctly
Transferred
REFM
REFMFR
SYNM
SYNMFR
LT
LTFR
Any
Frame_Sync
GM
GMFR
Add
LOF
LOFFR
LOF
LOFFR
Subtract
16
7
LGM
LGMFR
GM
GMFR
For Reception of Ref. Msg.
For Transmission of Ref. Msg.
Frame-Sync
of Ref. Msg
16
7
16
7
16
7
16
7
16
7
16
7
