External Core Complex Interfaces
e200z3 Power Architecture Core Reference Manual, Rev. 2
Freescale Semiconductor
7-53
shows another example of error termination.
Figure 7-24. Data Read with Error, Data Write Retracted, Instruction Read, Full Pipelining
The first read request (addr
x
) is taken at the end of cycle C1 because the bus is idle. It is a data read.
The second request (write to 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 retracts the requested access to addr
y
by driving
p_[d,i]_htrans signals to the IDLE state during the second cycle of the two-cycle error response.
A different access to addr
z
is requested during C4 and is taken at the end of C4. During C5, read data is
supplied for the addr
z
read, and the access is terminated normally.
In this example of error termination, a subsequent access was aborted.
nonseq
nonseq
idle
nonseq
idle
addr x
addr y
addr z
single
single
single
data x
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
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