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Message
From: NansonHuang at ITRI.ORG.TW<NansonHuang@I...>
Date: Thu Dec 18 13:43:35 CET 2003
Subject: [oc] Register Allocation Problems ?
hi,
Now I am thinking a problem. If there are 5 parameters needed assigned to
the register for example on AMBA-AHB or Wishbone, processor could control
the module via R/W the 5 parameters. Thus, we need to deal with the
register alocation to define the register. It comes up with such many ways
to assign each parameter to a 32-bits wide
register. If A paramater is 1 bit, B is 2 bits, C is 9 bits, D is 7 bits, E
is 16 bits,
should we put as many as bits in one 32-bits register, i.e. to increase the
register density for less register access ? However, the driver needs to
pack or unpack the registers to extract/put the information it need. It
also takes time and slow down the
response time of the driver. What's the generally way to deal with it ? How
to balance it ? Should we divided the 32-bits register as 4 or 8 -bits per
block and just put one parameter to it for easy s/w decode ? For example,
0000000A000000B0000000C as a 32-bits register where A is 1-bit, B is 2
bits, C is 9-bits.
Appreciate for your any comments. Thanks
Nanson
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