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Applies to: AHB
My AHB system contains an ARM1136 which uses ARMv6 AHB-Lite extension signals. How do I use these signals?
The signals in question are:
HRESP, HPROT[4:2], HPROT, HUNALIGN, HBSTRB[7:0],HSIDEBAND and HSIDEBAND[3:1]
The purpose of the signals and how to use them is shown below:
This indicates an exclusive access has failed and is an input to the
core. Since there is no provision for Exclusive Access in an AMBA 2.0
system (AHB), this signal is not used and can therefore be tied HIGH.
Indicates memory type. These are outputs and, if your memory system
doesn't require this information, you may ignore these signals.
Indicates an exclusive access and is an output. Leave unconnected.
Quote from the TRM: "This signal is only provided to assist with
backwards compatibility and indicates when a single unaligned transfer
occurs that requires more than one AHB v2.0 transfer without byte
strobes. The HUNALIGN signal has address phase timing and must be
asserted HIGH for unaligned transfers and LOW for AHB v2.0 compatible
aligned transfers.". You can therefore leave it unconnected, provided
you will not be making any unaligned transfers.
Again, these are for use with unaligned transfers and indicate which
byte lanes are active during a transfer. An AMBA v2.0 system should not
make use of them so you can leave them unconnected.
HSIDEBAND and HSIDEBAND[3:1]
These indicate the type of memory being accessed and are not applicable
in an AMBA v2.0 memory system. Leave unconnected.
Basically, all the signals can be left unconnected with the exception of
HRESP which is an input and should be tied HIGH, PROVIDING the core
is in backwards-compatible mode (the default at reset) and no attempt is
made to change into BE-8 bigendianness.
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