Enhanced Time Processing Unit (eTPU2)
29-6
Freescale Semiconductor
PXR40 Microcontroller Reference Manual, Rev. 1
In addition to the predefined channel configurations above, the user can also program its own channel
configuration, defining how input captures, matches and service-requests are related.
29.1.1.1.3
Host Interface
The Host interface allows the Host CPU to control the operation of the eTPU. The Host CPU must
initialize the eTPU by writing to the appropriate Host interface registers to assign a Function and priority
to each channel. In addition, the Host writes to the Host Service Request and channel configuration
registers to further define Function operation for each initialized channel. Refer to
for a detailed description.
When the SCM is implemented by RAM, the Host must first initialize it with the proper microcode
program prior to enabling any eTPU Function, and then enable eTPU access (which also disables Host
access).
29.1.1.1.4
Shared Data Memory - SDM
The SDM works as data RAM which can be accessed by the Host CPU and up to two eTPU Engines. This
memory is used for information transfer between the Host CPU and the eTPU, as data storage for the eTPU
microcode program or for communication between the two eTPU Engines. SDM width is 32 bits, and is
accessible by the Host as byte, 16-bit or 32-bit wide. eTPU can access it as full 32-bits, lower 24-bits or
upper byte (8-bit).
The host can also access the SDM space mirrored in other area with Parameter Signal Extension (PSE).
Parameter Signal Extension accesses differ from the usual host accesses to the original SDM area as
follows:
•
Writes are effective only to the lower 3 bytes of a word: the word’s most significant byte is kept
unaltered in SDM.
•
Reads return the lower 3 bytes of a word sign-extended to 32 bits, i.e.: the most significant bit of
the word s 2nd most significant byte is copied in all 8 bits of the most significant read byte.
Each eTPU channel can be associated with a variable number of parameters located in the SDM, according
to its selected Function. In addition, the SDM can be fully shared between two eTPU Engines, enabling
direct communication between them.
High flexibility of the SDM utilization is achieved as follows:
•
Each channel has a programmable base address pointing to the address of its first parameter with
two parameter granularity. This way the SDM can be partitioned according to the actual function
needs.
•
The microcode can access the first 128 parameters of the selected channel in channel relative
access mode.
•
Each Engine can access all the SDM address space in indirect addressing mode. Blocks of data are
easily transferred using stack operation.
•
Absolute addressing mode can access the first 256 parameters (TPU3 functionality), implementing
a shared pool of parameters holding global variables.
Summary of Contents for PXR4030
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Page 120: ...Signal Descriptions 3 54 Freescale Semiconductor PXR40 Microcontroller Reference Manual Rev 1...
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