
Page 8
Programming Details
Chapter 3
Page 8
01270193.doc
Blue Chip Technology Ltd.
The Analogue Conversion Control Register at Base 2 + 0C
h
is used to specify
the type of conversion to be performed. The functions of the bits within this
register are described below:-
Analogue Conversion Control Register
Bit no.
b4..b2
Conversion trigger:-
(Base 2 + 0C
h
) Read/write.
Function
000 = No trigger
001 = Software trigger
010 = PC0 input port line
011 = PC3 input port line
100 = Counter/timer 0 output (see Note)
101 = Counter/timer 1 output (see Note)
110 = Counter/timer 2 output (see Note)
111 = Not used.
0 = edge triggered (single conversion)
1 = level triggered (multiple conversions)
0 = Manual selection of single channel
1 = Automatic selection & increment
b1
Conversion Trigger mode:-
b0
Input Channel Selection:-
Note:
Triggers from the counter / timer outputs occur on the high-to-low
transition of the output. Most counter / timer modes operate in this
manner.
If manual selection of the input channel is set, then a conversion of the channel
specified in the Analogue Input Select Register, will be performed whenever a
trigger condition occurs.
The trigger condition may be selected from the list shown in the table. For all
trigger modes, it is necessary to select whether the trigger is edge or level
triggered.
If edge trigger is selected, then a new conversion will not occur until the trigger
(from whatever source) has been negated and re-asserted i.e. the conversion is
initiated on the low to high transition of the trigger source. This ensures that
only one conversion takes place.
If level trigger is selected, then conversions will be performed for as long as the
trigger source is present.