TC1796
Peripheral Units (Vol. 2 of 2)
Analog-to-Digital Converter (ADC)
User’s Manual
25-5
V2.0, 2007-07
ADC, V2.0
25.1.2
Conversion Request Sources
The ADC module control logic provides effective methods to request and arbitrate
conversions. Conversion requests for one or more analog channels can be triggered by
hardware as well as by software to provide maximum flexibility in requesting A/D
conversions. Up to six individual configurable conversion request sources are
implemented to issue A/D conversion requests.
In principle, the conversion request sources can be assigned either to the group of
parallel conversion request sources or the group of sequential conversion request
sources. A global overview of parallel and sequential conversion request sources and
detailed descriptions of each source are provided in the following sections.
25.1.2.1 Parallel Conversion Request Sources
Parallel conversion request sources generate one or more conversion request at a time
for the analog channels.
shows the available parallel conversion request
sources including the associated control and status signals.
A parallel conversion request source is controlled by a control register, a request
pending register, an arbitration participation flag, and the source arbitration level.
Each parallel conversion control register contains 16 bits defining whether a conversion
request is activated for a specific channel. The contents of the parallel conversion control
register are loaded into the conversion request pending register on request source
specific trigger events. If at least one bit is set in the conversion request pending register,
the arbitration participation flag is set for this source. This informs the arbiter to include
this parallel conversion request source into arbitration.
If a parallel conversion request source is the arbitration winner, a conversion is started
for the conversion request within the conversion request pending register with the
highest channel number. Starting a conversion causes the conversion request bit in the
conversion request pending register to be cleared by the arbiter. If a currently running
conversion initiated by the parallel source is cancelled, the arbiter restores the
corresponding conversion request bit in the conversion request pending registers for this
Table 25-1
Parallel Conversion Request Sources
Request
Source
Control
Register
Conversion
Req. Pending
Register
Arbitration
Participation
Flag
Source
Arbitration
Level
Timer
TTC
TCRP
AP.TP
SAL.SALT
External Event
EXTC
EXCRP
AP.EXP
SAL.SALEX
Software
REQ0
SW0CRP
AP.SW0P
SAL.SALSW0
Auto-Scan
SCN
ASCRP
AP.ASP
SAL.SALAS