Datasheet

Element1 Element2
Frame 1
Element3
Element4
Frame 2
Element5 Element6
Frame 3
Element7 Element8
Frame 4
HTUREQ HTUREQ HTUREQ
HTUREQ
Element Count =2
Frame count =4
Control
Memory Protection
FIFO
HTU
NHET
Data
Data
Address
Normal
Request
Quiet
Request
8
8
Control Packet
RAM
with Parity
SCR
2
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Module Operation
Figure 24-2. HTU Block Diagram
Transfers between NHET RAM and the main memory are triggered by 8 different normal NHET requests.
Quiet requests are used for specific cases and are discussed in Section 24.2.4.1. Control packets, which
store the source and destination addresses, the transfer count and other information (see Section 24.5),
are associated with the requests. A FIFO decouples the read- and write-path and allows to do data-
packing in the case of different read- and write-data sizes. The application can specify a section of
memory into or from which the data is transferred. This serves as memory protection in the case that
information in the control packet RAM was unintentionally altered and avoids that the HTU can overwrite
important application data.
Control packets are implemented as double control packets (DCP) which allow to specify two buffers for
the data transfer. This enables the CPU to work with one buffer, while new data is transferred to/from the
other buffer.
The control packet defines:
the start address of the source/destination buffers
the NHET instruction address location
how many elements need to be transferred
the buffer handling
A transfer is triggered when a certain condition (for example, capture, compare condition) is detected by a
NHET instruction. The NHET instruction specifies which request line to the HTU will be triggered at the
event. The DCPs have a fixed assignment to the request lines and the corresponding assignment can be
found in the device datasheet. Once a request is triggered, it starts a frame transfer. A frame can contain
one or more elements. Elements are defined as 32-bit or 64-bit words of data.
Figure 24-3. Example of a HTU Transfer
1067
SPNU562May 2014 High-End Timer Transfer Unit (HTU) Module
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