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TC1796
System Units (Vol. 1 of 2)
On-Chip System Buses and Bus Bridges
User’s Manual
6-26
V2.0, 2007-07
Buses, V2.0
•
The Error Data Capture Registers (xBCU_EDAT) stores the 32-bit FPI Bus data bus
information that has been captured during the erroneous FPI Bus transaction.
•
The Error Control Capture Register (xBCU_ECON) stores status information of the
bus error event.
If more than one FPI Bus transaction generates a bus error, only the first bus error is
captured. After a bus error has been captured, the capture mechanism must be released
again by software.
If a write transaction from TriCore causes an error on the SPB, the originating master is
not informed about this error as it is not an SPB master agent. With each bus error-
capture event, a service request is generated, and an interrupt can be generated if
enabled and configured in the corresponding service request register.
Interpreting the BCU Control Register Error Information
Although the address and data values captured in registers xBCU_EADD and
xBCU_EDAT, respectively, are self-explanatory, the captured FPI Bus control
information needs some more explanation.
Register xBCU_ECON captures the state of the read (RDN), write (WRN), Supervisor
Mode (SVM), acknowledge (ACK), ready (RDY), abort (ABT), time-out (TOUT), bus
master identification lines (TAG) and transaction operation code (OPC) lines of the
FPI Bus.
The SVM signal is set to 1 for an access in Supervisor Mode and set to 0 for an access
in User Mode.The time-out signal indicates if there was no response on the bus to an
access, and the programmed time (via xBCU_TOUT) has elapsed. TOUT is set to 1 in
this case. An acknowledge code has to be driven by the selected slave during each data
cycle of an access. These codes are listed in
Each master on the FPI Bus is assigned a 4-bit identification number, the master TAG
number (see
). This makes it possible to distinguish which master has
performed the current transaction.
Table 6-10
FPI Bus Acknowledge Codes
Code (ACK)
Description
00
B
NSC: No Special Condition.
01
B
SPT: Split Transaction (not used in the TC1796).
10
B
RTY: Retry. Slave can currently not respond to the access. Master
needs to repeat the access later.
11
B
ERR: Bus Error, last data cycle is aborted.