3.2.9.2 Controlling and Monitoring the Digital Compare Submodule
The digital compare submodule operation is controlled and monitored through the following registers.
Table 3-20. Digital Compare Submodule Registers
Register
Address Offset
Shadowed
Description
Bit Description
TZDCSEL
0x13
No
Trip Zone Digital Compare Select Register
0x30
No
Digital Compare Trip Select Register
0x31
No
Digital Compare A Control Register
0x32
No
Digital Compare B Control Register
0x33
No
Digital Compare Filter Control Register
DCCAPCTL
0x34
No
Digital Compare Capture Control Register
DCFOFFSET
0x35
Writes
Digital Compare Filter Offset Register
DCFOFFSETCNT
0x36
No
Digital Compare Filter Offset Counter Register
DCFWINDOW
0x37
No
Digital Compare Filter Window Register
DCFWINDOWCNT
0x38
No
Digital Compare Filter Window Counter Register
DCCAP
0x39
Yes
Digital Compare Counter Capture Register
(1)
The TZDCSEL register is part of the trip-zone submodule but is shown here because of its functional significance to the digital
compare submodule.
(2)
These registers are EALLOW protected and can be modified only after executing the EALLOW instruction. For more information, see
the
System Control and Interrupts
chapter.
3.2.9.3 Operation Highlights of the Digital Compare Submodule
The following sections describe the operational highlights and configuration options for the digital compare
submodule.
3.2.9.3.1 Digital Compare Events
earlier in this section, trip zone inputs (TZ1, TZ2, and TZ3) and COMPxOUT signals
from the analog comparator (COMP) module can be selected via the DCTRIPSEL bits to generate the Digital
Compare A High and Low (DCAH/L) and Digital Compare B High and Low (DCBH/L) signals. Then, the
configuration of the TZDCSEL register qualifies the actions on the selected DCAH/L and DCBH/L signals, which
generate the DCAEVT1/2 and DCBEVT1/2 events (Event Qualification A and B).
Note
The TZn signals, when used as a DCEVT tripping functions, are treated as a normal input signal and
can be defined to be active high or active low inputs. EPWM outputs are asynchronously tripped when
either the TZn, DCAEVTx.force, or DCBEVTx.force signals are active. For the condition to remain
latched, a minimum of 3*TBCLK sync pulse width is required. If pulse width is < 3*TBCLK sync pulse
width, the trip condition may or may not get latched by CBC or OST latches.
The DCAEVT1/2 and DCBEVT1/2 events can then be filtered to provide a filtered version of the event signals
(DCEVTFILT) or the filtering can be bypassed. Filtering is discussed further in
DCAEVT1/2 and DCBEVT1/2 event signals or the filtered DCEVTFILT event signals can generate a force to the
trip zone module, a TZ interrupt, an ADC SOC, or a PWM sync signal.
•
force signal:
DCAEVT1/2.force signals force trip zone conditions which either directly influence the output
on the EPWMxA pin (via TZCTL[DCAEVT1 or DCAEVT2] configurations) or, if the DCAEVT1/2 signals are
selected as one-shot or cycle-by-cycle trip sources (via the TZSEL register), the DCAEVT1/2.force signals
can effect the trip action via the TZCTL[TZA] configuration. The DCBEVT1/2.force signals behaves similarly,
but affect the EPWMxB output pin instead of the EPWMxA output pin.
The priority of conflicting actions on the TZCTL register is as follows (highest priority overrides lower priority):
– Output EPWMxA: TZA (highest) -> DCAEVT1 -> DCAEVT2 (lowest)
– Output EPWMxB: TZB (highest) -> DCBEVT1 -> DCBEVT2 (lowest)
Enhanced Pulse Width Modulator (ePWM) Module
298
TMS320x2806x Microcontrollers
SPRUH18I – JANUARY 2011 – REVISED JUNE 2022
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