TC1796
System Units (Vol. 1 of 2)
Direct Memory Access Controller
User’s Manual
12-23
V2.0, 2007-07
DMA, V2.0
12.1.7
On-Chip Debug Capabilities
The DMA controller in the TC1796 provides some debugging capabilities. These debug
features support:
•
Hard-suspend Mode of the DMA controller (for test purposes only)
•
Soft-suspend Mode of DMA channels
•
Break signal generation
•
Trace signal generation
In suspend modes, the operations of DMA channels or the complete DMA module are
stopped. Under certain condition conditions also a break signal is generated for the on-
chip debug support logic. Further, DMA trace information can be output.
12.1.7.1 Hard-suspend Mode
In Hard-suspend Mode, the DMA controller module clock
f
DMA
is switched off and all
further module actions are disabled. Module registers cannot be written anymore in
Hard-suspend Mode, but combinatorial read operations of the module registers are still
possible. Hard-suspend Mode of the DMA controller can be entered either by an active
module suspend request signal (generated by hardware) or by writing the clock control
register DMA_CLC register with an appropriate value.
When switching the DMA controller module clock
f
DMA
off, the communication of the
DMA controller via its Bus Switch is blocked. Hard-suspend Mode can only be left by a
reset operation.
Attention: The Hard-suspend Mode is mainly applicable for test purposes only. It
can only be exit by a reset operation, and should not be used during
normal operation of the DMA controller.
12.1.7.2 Soft-suspend Mode
The TC1796 on-chip debug control unit is able to generate a Soft-suspend Mode request
(SUSREQ) for the DMA controller. When this soft suspend request becomes active, the
state of a DMA channel becomes frozen, DMA requests are no longer forwarded, and
the state of the DMA channel can be analyzed by reading the register contents.
Soft-suspend Mode of DMA channel mn is entered if its suspend enable bit SUSENmn
in the Suspend Mode Register SUSPMR is set. When SUSREQ becomes active, the
operation of all DMA channels mn that are enabled for Soft-suspend Mode is stopped
automatically after its current DMA transfers have been finished in the transaction control
unit. Afterwards, the suspend active status flag SUSPMR.SUSACmn is set, indicating
that DMA channel mn is in Soft-suspend Mode. DMA channels that are disabled for
Suspend Mode (SUSENmn = 0) continue with their normal operation.
In Soft-suspend Mode, register contents can be modified. These modifications are taken
into account for further DMA transactions or DMA transfers of the related DMA channel