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Re: [avr-libc-dev] New device support
From: |
Dmitry K. |
Subject: |
Re: [avr-libc-dev] New device support |
Date: |
Sun, 15 Jul 2007 17:40:02 +1100 |
User-agent: |
KMail/1.5 |
On Saturday 14 July 2007 08:55, Joerg Wunsch wrote:
[...]
> The question now is, what to chose for the name of TCCR0B when it's
> defined as the union/bitfield sketched out above? If we call that
> TCCR0B, the old way of handling TCCR0B like
>
> TCCR0B = _BV(CS00) | _BV(CS02);
>
> would be rewritten as
>
> TCCR0B.byte = _BV(CS00) | _BV(CS02);
>
[...]
A small note: the above expressions are *different*.
The first is "to write the 0x05 value into TCCR0B" and
takes 2 clocks (ldi,out). But the second is "to read TCCR0B,
clear 0x07 field, add 0x05 value and write back to TCCR0B"
and takes 4 clocks (in,andi,ori,out).
Simetimes the such rewriting is wrong, for registers that
contain bits which are cleared by writing of "1" (like
UCSR0A).
Nevertheless I agree, that the existing approach is fraught
with mistakes as Atmel sometimes transfers bits from one register
to another (for example, SE is moved from MCUSR to SMCR).
Dmitry.
- Re: [avr-libc-dev] New device support, (continued)
RE: [avr-libc-dev] New device support, Eric Weddington, 2007/07/14
Re: [avr-libc-dev] New device support,
Dmitry K. <=
- Re: [avr-libc-dev] New device support, Bob Paddock, 2007/07/15
- Re: [avr-libc-dev] New device support, Joerg Wunsch, 2007/07/15
- Re: [avr-libc-dev] New device support, Bob Paddock, 2007/07/17
- Re: [avr-libc-dev] New device support, Joerg Wunsch, 2007/07/18
- [avr-libc-dev] Hint For Watchdog Disable on Newer AVRs in the Manual, Harald Kipp, 2007/07/18
- Re: [avr-libc-dev] Hint For Watchdog Disable on Newer AVRs in the Manual, Harald Kipp, 2007/07/18
- Re: [avr-libc-dev] Hint For Watchdog Disable on Newer AVRs in the Manual, Joerg Wunsch, 2007/07/18
- Re: [avr-libc-dev] Hint For Watchdog Disable on Newer AVRs in the Manual, Harald Kipp, 2007/07/19
Re: [avr-libc-dev] New device support, Joerg Wunsch, 2007/07/15