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ADC.11:
Modifications of ADM field while bit ADST = 0
The A/D converter may unintentionally start one auto scan single conversion sequence when the
following sequence of conditions is true:
(1) the A/D converter has finished a fixed channel single or continuous conversion of an analog
channel n > 0 (i.e. contents of ADCON.ADCH = n during this conversion)
(2) the A/D converter is idle (i.e. ADBSY = 0)
(3) then the conversion mode in the ADC Mode Selection field ADM is changed to Auto Scan Single
(ADM = 10b) or Continuous (ADM = 11b) mode without setting bit ADST = 1 with the same
instruction
Under these conditions, the A/D converter will unintentionally start one auto scan single conversion
sequence, beginning with channel n-1, down to channel number 0.
In case the channel number ADCH has been changed before or with the same instruction which
selected the auto scan mode, this channel number has no effect on the unintended auto scan
sequence (i.e. it is not used in this auto scan sequence).
Note:
When a conversion is already in progress, and then the configuration in register ADCON is changed,
-
the new conversion mode in ADM is evaluated after the current conversion
-
the new channel number in ADCH and new status of bit ADST are evaluated after the current
conversion when a conversion in fixed channel conversion mode is in progress, and after the
current conversion sequence (i.e. after conversion of channel 0) when a conversion in an auto scan
mode is in progress.
In this case, it is a specified operational behaviour that channels n-1 .. 0 are converted when ADM is
changed to an auto scan mode while a fixed channel conversion of channel n is in progress (see e.g.
C167 User's Manual, V2.0, p16-4)
Workaround:
When an auto scan conversion is to be performed, always start the A/D converter with the same
instruction which sets the configuration in register ADCON.
X9:
Read Access to XPERs in Visible Mode
The data of a read access to an XBUS-Peripheral (XRAM, CAN) in Visible Mode is not driven to the
external bus. PORT0 is tristated during such read accesses.
Semiconductor Group
Errata Sheet, C167CR-LM, ES-DB, DB, 1.1, Mh
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