TC1796
Peripheral Units (Vol. 2 of 2)
Analog-to-Digital Converter (ADC)
User’s Manual
25-8
V2.0, 2007-07
ADC, V2.0
25.1.2.3 Parallel Conversion Request Source “Timer”
Periodic samples can be achieved by timer generated conversion requests. A
programmable timer serves as trigger source. Service request generation logic as well
as the arbitration lock mechanism are provided to ensure periodical sampling without
jitter. The block diagram of the timer and its control and status blocks are shown in
Figure 25-4 Block Diagram of Conversion Request Source “Timer”
When the timer run bit is set, the timer is clocked with
f
TIMER
, which is derived from the
arbiter. This synchronizes the timer on the arbiter for jitter-free sampling. If the timer run
bit TCON.TR becomes set, the timer bit field TSTAT.TIMER is loaded with the timer
reload value TCON.TRLD. With each clock cycle of
f
TIMER
, the timer register is
decremented and compared to the arbitration-lock-boundary value TCON.ALB. If the
value of the timer register is equal to the value of the arbitration-lock-boundary, the
arbitration lock bit STAT.AL is set (see
). This arbitration-lock mechanism
can be used to generate samples without being delayed by a currently running
conversion. When the timer = 0, the arbitration is unlocked, the timer register is
reloaded, the arbitration lock bit is cleared, the timer related service request status flag
(MSS1.MSRT) is set, and a trigger pulse is sent to the conversion request source
“Timer”.
MCB06007
TCON.TRLD
14
TSTAT.TIMER
Compare
Request
Generation
and
Arbitration
Lock
Match
Service Req.
Generation
Set TCON.TR
TCON.ALB
Clock
from Arbiter
f
TIMER
-1
TCON.TR
Set
Clear
Timer = 0 or
14
14