Intel
®
81341 and 81342 I/O Processors
December 2007
Developer’s Manual
Order Number: 315037-002US
513
Application DMA Unit—Intel
®
81341 and 81342
5.12
Internal Interface Parity Checking and Generation
The south internal bus interface of the ADMA supports byte-wise parity on both the
address bus and data bus. The ADMA can act as both an initiator and a target on the
south internal bus. The ADMA acts as a target when its memory-mapped registers are
being accessed from the south internal bus. The ADMA acts as an initiator when it
fetches descriptors or while transferring data. Note that the ADMA fetches descriptors
via the south internal bus, and the descriptors are normally located in the DDR
memory.
As a target when the ADMA memory-mapped registers are being accessed, the ADMA
behavior is described as follows:
• For a write request, the ADMA internal bus interface checks the address parity
during the address request phase, asserts the internal bus error signal when it
detects an address parity error. The address parity error is logged by the System
Controller. Refer to the
Chapter 6.0, “System Controller (SC) and Internal Bus
. However, during the data phase of a write request, the ADMA does
not
check the data parity.
• For a write request, the ADMA internal bus interface checks the address parity
during the address request phase, asserts the internal bus error signal when it
detects an address parity error. The address parity error is logged by the System
Controller. Refer to the
Chapter 6.0, “System Controller (SC) and Internal Bus
. When returning data during read completions, the ADMA simply forwards
the data and parity generated by the DMCU on the south internal bus.
As an initiator the ADMA behavior is as follows:
• To issue a read request on the internal bus, the ADMA generates address parity
before driving the address on the internal bus. When receiving data during a read
completion, the ADMA forwards the data and parity to the DMCU. For example, the
ADMA does
not
verify the data parity. However, when receiving data during a read
completion for a descriptor fetch, the ADMA verifies the parity on the descriptor
data. When a data parity error is detected, the ADMA flags the parity error.
• To issue a write request on the internal bus, the ADMA generates the address parity
before driving the address on the south internal bus. For data, the ADMA does
not
generate data parity, it simply forwards the data and parity as received from the
DMCU.
Note:
The Memory Port Interface of the ADMA does not verify or generate parity.
Figure 75. Logical Data Access Paths with Parity Protection
Internal Bus
Interface
Data_in
Address
Address Parity
Data_in Parity
Data_out Parity
Data_out
ADMA
B6237-01