User`s guide

SROM Mini-Debugger Command Set 3–27
User Commands
fr
The follow-with-read (fr) command toggles the follow-with-read flag, enabling or
disabling the execution of a read operation after the last operation executed by a
command.
Control Flags
fw (follow-with-write flag)
Description
The follow-with-read command is an advanced command whose use is required in
certain situations where a second operation is needed to achieve a desired result,
such as continuously creating a cache victim or having an I/O read operation
interspersed between memory writes. Enabling the follow-with-read flag causes a
prompt for an additional address from which the read operation is performed, unless
the follow-with-write flag is also enabled. In this case, the additional address is used
for the write operation and the read operation is performed from the first address.
The read operation takes place at the end of the command sequence, but after all read
and write operations required by the current command have executed (including any
write operations due to the follow-with-write flag being enabled). The data read may
or may not be displayed, depending on the current command.
The default state is off.
Example
In the following example, a memory hierarchy composed of a 2MB direct-mapped,
write-back, read-allocate cache and system memory is assumed. This may be the
case in a 21064-based system where the Dcache is off and an external 2MB cache is
on.
To continuously write the same address and guarantee that the data makes it to the
system memory and is not simply cached, you must create a victim after each write
operation. To create a victim, map the read address to the same cache index as the
write operation.