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External Core Complex Interfaces
e200z3 Power Architecture Core Reference Manual, Rev. 2
7-52
Freescale Semiconductor
shows an example of error termination.
Figure 7-23. Read and Write Transfers: Instruction Read with Error, Data Read, Write,
Full Pipelining
The first read request (addr
x
) is taken at the end of cycle C1 because the bus is idle. It is an instruction
prefetch.
The second read request (addr
y
) is not taken at the end of C2 because the first access is still outstanding
(no p_[d,i]_hready assertion). An error response is signaled by the addressed slave for addr
x
by driving
ERROR onto the p_[d,i]_hresp[2:0] inputs. This is the first cycle of the two cycle error response protocol.
p_[d,i]_hready is asserted during C3 for the first read access (addr
x
) while the ERROR encoding remains
driven on p_[d,i]_hresp[2:0], terminating the access. The read data bus is undefined.
In this example of error termination, the CPU continues to request an access to addr
y
. It is taken at the end
of C3. During C4, read data is supplied for the addr
y
read, and the access is terminated normally during C4.
Also during C4, a request is generated for a write to addr
z
, which is taken at the end of C4 because the
second access is terminating.
Data for the addr
z
write cycle is driven in C5, the cycle after the access is taken.
During C5, a ready/OKAY response is signaled to complete the write cycle to addr
z
.
In this example of error termination, a subsequent access remained requested. This does not always occur
when certain types of transfers are terminated with error. The following figures outline cases where an
error termination for a given cycle causes a pending request to be aborted prior to initiation.
nonseq
nonseq
nonseq
idle
addr x
addr y
addr z
single
single
single
data x
data y
data z
okay
error
error
okay
okay
1
2
3
4
5
6
m_clk
p_htrans
p_addr,p_hprot
p_hsize
,
p_hbstrb
, etc
p_hburst
p_hunalign
p_hwrite
p_hrdata
p_hwdata
p_hready
p_hresp
Содержание e200z3
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