Posted by GA on November 20, 2002, 12:50:19 With regard to the strange behavior you are seeing. Have you got the AVcc, AVss and AVref connected correctly, i.e. not floating. Also, are you clearing the ADF flag before starting the conversion and waiting until it is set before reading the conversion result? Make sure that the conversion time is at least 6.7us which means for a CPU frequency greater than 20MHz CKS in the ADCSR register must be 0. If you are still seeing problems I think I might have some code using the ADC. GA. --Previous Message--
194.131.190.3
ADDRA0 can be read as either bytes or as a word. When reading as bytes the upper byte must be read first. Just read it for word access.
: Hello,
: Re: Section 16.3 of SH7040 Series
: Hardware Manual ADE-602-117D
: Rev.5.0 3/19/00
: In Section 16.3, 'Interface with the
: CPU', on page 573, it gives the
: impression that ADDRA0 must be,
: and can only be, read correctly in
: byte size. Then a few lines later
: it says 'In addition, when reading
: ADDR in word size, upper byte is
: automatically read before the
: lower byte.'
: There may be an ambiguity or
: contradiction here? I am having
: trouble reading an A/D Conversion
: result from ADDRA0.
: Also, I think I am having some
: strange behaviour of the mid-speed
: A/D0 module. I input 2Vdc to
: channel AN1. When I run a sort
: program to make a single A/D
: conversion, the first result in
: ADDRB0 is reasonably correct, but
: if I run the program again from
: reset a few times in quick
: succession, the results climbs up
: and eventually stops at maximum
: FFC. If I wait a minute or so and
: run again, the result drops down,
: but then climbs up to FFC again
: with a few quick runs from reset.
: I have tried channels AN0 and AN1
: and behaviour is same. The I/P
: voltage is very constant at 2Vdc
: on the CRO.
: Anyone experienced this behaviour? or
: can anyone offer any advice?
: Regards,
: John O'Connor
:
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