[sdiy] IIR Shift Filter problem - help with bug spotting in PIC ASM

[Scott Gravenhorst]

Tom Wiltshire <tom at electricdruid.net> wrote:
>Oh, I dunno so much, Scott. I've found their documentation pretty good =
>in general. When you actually dig into it, it's there in black and white =
>as Steve posted. The problem is *finding* the exact little sub-paragraph =
>that deals with whatever issue you're looking at without losing two days =
>doing it!

That's what I mean, right there...  Not bashing at all, it's just frustrating,

>I suppose there's a there's a trade-off between "detailed" and =
>"concise". That's a tough balance to find.
>
>On 10 Mar 2017, at 16:11, Scott Gravenhorst <music.maker at gte.net> wrote:
>
>>=20
>> This is a complaint I've also had about much of Microchip's =
>documentation.  I love the
>> parts they make, but they could do better with documentation clarity.
>>=20
>> steve at bendentech.co.uk wrote:
>>> You are right. The datasheet description of the STATUS register is a =
>bit =3D
>>>=20
>>> misleading. It says:
>>>=20
>>> "If the STATUS register is the destination for an instruction that =3D
>>>=20
>>> affects the Z, DC or C bits, then the write to these three bits is
>>> disabled."
>>>=20
>>> Because XORWF only affects the Z bit, a natural assumption is that =
>the C =3D
>>>=20
>>> and CD bits should still be accessible (helped by the Instruction Set =
>=3D
>>>=20
>>> Summary labelling the relevant column as "Status Affected", implying =
>=3D
>>>=20
>>> that those not listed are not affected).
>>>=20
>>> However, it would appear that what they should have said is:
>>>=20
>>> "If the STATUS register is the destination for an instruction that =3D
>>>=20
>>> affects ANY OF the Z, DC or C bits, then the write to ALL THREE bits =
>is =3D
>>>=20
>>> disabled."
>>>=20
>>> i.e. because the XORWF is affecting Z, writes to Z, DC and C are all =
>=3D
>>>=20
>>> blocked.
>>>=20
>>> The more I read it now, the more obvious it is, but it wasn't obvious =
>=3D
>>>=20
>>> before!
>>>=20
>>> Yey! I can stop thinking about this now :-)
>>>=20
>>> Steve L.
>>=20
>>=20
>> -- ScottG
>> =
>________________________________________________________________________
>> -- Scott Gravenhorst
>> -- http://scott.joviansynth.com/
>> -- When the going gets tough, the tough use the command line.
>> -- Matt 21:22
>>=20
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>
>

-- ScottG
________________________________________________________________________
-- Scott Gravenhorst
-- http://scott.joviansynth.com/
-- When the going gets tough, the tough use the command line.
-- Matt 21:22