Страница 1 мировой engineering стандарты общая спецификация

Page 229
GM WORLDWIDE ENGINEERING STANDARDS
GMW3110
© Copyright 2010 General Motors All Rights Reserved
February 2010
Page 229 of 336
The following function, DecrementPDS_Counters, is used to decrement the loop counters associated with
each DPID in the PDS. The loop counters are used to determine when a DPID is ready for transmission. This
function is called from the Send_AA_Periodic_Msgs() function and also from the Process_AA_Msgs() function.
BEGINFUNCTION DecrementPDS_Counters()
FOR (PDS_Index ←
$00 TO (PDS_Length - $01) BY $01)
IF ((PDS[PDS_Index].DPID!=$00) AND (PDS[PDS_Index].Transmit_Count>$00)) THEN
PDS[PDS_Index].Transmit_Count←(PDS[PDS_Index].Transmit_Count-$01)
ENDIF
ENDFOR
IF (Num_Loops_Since_Periodic < Min_Loops_Since_Periodic) THEN
Num_Loops_Since_Periodic ←
(Num_Loops_Since_Periodic + $01)
ENDIF
ENDFUNCTION
The following function, ClearAndDisablePDS, is called by this and other services to stop and clear the PDS
BEGINFUNCTION ClearAndDisablePDS()
FOR (PDS_Index ←
$00 TO (PDS_Length -$01) BY $01)
PDS[PDS_Index].DPID ←
$00
ENDFOR
PDS_Number_Active ←
$00
PDS_Xmit_Index ←
$00
8.19.6.3 Graphical and Tabular Examples of Mode $AA Periodic Scheduled Rates. 
This section contains
two examples of scheduled periodic data. Each example contains a graphical depiction of what messages are
transmitted on the bus, followed by a table which shows the PDS variables and how they change each time the
Process_AA_Msgs() function is executed. In the examples below, the following information is given:
•
The fast rate is 25 ms.
•
The medium rate is 200 ms for Figure 34.
•
The medium rate is 300 ms for Figure 35.
•
The Process_AA_Msgs() function is executed every 12.5 ms (AA_Msg_Rate = 12.5 ms).
•
The PDS can hold a maximum of four scheduled items.
•
It is possible to send a DPID any time its counter has expired (Min_Loops_Since_Periodic = 0).
Since the AA_Msg_Rate is 12.5 ms, the fast rate loop counter would be set to 2 (this value is based on the
scheduled rate (25 ms) divided by the AA_Msg_Rate (12.5 ms) or 25/12.5) each time a fast rate DPID is sent
and the medium rate loop counter is reset to 16 (or 24) (scheduled rate divided by AA_Msg_Rate or 200
(or 300)/12.5) each time a medium rate DPID is sent.
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