Chapter 18 Enhanced Direct Memory Access (eDMA)
MPC5602P Microcontroller Reference Manual, Rev. 4
414
Freescale Semiconductor
read_ws — wait states seen during the system bus read data phase
write_ws — wait states seen during the system bus write data phase
exit — channel shutdown (three cycles)
For example: consider a system with the following characteristics:
•
Internal SRAM can be accessed with one wait-state when viewed from the system bus data phase.
•
All slave reads require two wait-states, and slave writes three wait-states, again viewed from the
system bus data phase.
•
System operates at 150 MHz.
For an SRAM to slave transfer,
PEAKreq = 150 MHz / [4 + (1 + 1) + (1 + 3) + 3] cycles = 11.5 Mreq/sec
Eqn. 18-2
For an slave to SRAM transfer,
PEAKreq = 150 MHz / [4 + (1 + 2) + (1 + 1) + 3] cycles = 12.5 Mreq/sec
Eqn. 18-3
Assuming an even distribution of the two transfer types, the average peak request rate is:
PEAKreq = (11.5 Mreq/sec + 12.5 Mreq/sec) / 2 = 12.0 Mreq/sec
Eqn. 18-4
The minimum number of cycles to perform a single read/write, zero wait states on the system bus, from a
cold start (no channel is executing, eDMA is idle) are the following:
•
11 cycles for a software (TCD.START bit) request
•
12 cycles for a hardware (eDMA peripheral request signal) request
Two cycles account for the arbitration pipeline and one extra cycle on the hardware request resulting from
the internal registering of the eDMA peripheral request signals. For the peak request rate calculations
above, the arbitration and request registering is absorbed in or overlap the previous executing channel.
NOTE
When channel linking or scatter/gather is enabled, a two-cycle delay is
imposed on the next channel selection and startup. This allows the link
channel or the scatter/gather channel to be eligible and considered in the
arbitration pool for next channel selection.
18.7
Initialization / application information
18.7.1
eDMA initialization
A typical initialization of the eDMA has the following sequence:
1. Write the EDMA_CR if a configuration other than the default is desired.
2. Write the channel priority levels into the EDMA_CPR
n
registers if a configuration other than the
default is desired.
3. Enable error interrupts in the EDMA_EEIRL and/or EDMA_EEIRH registers (optional).
Содержание SAFE ASSURE Qorivva MPC5601P
Страница 2: ...MPC5602P Microcontroller Reference Manual Rev 4 2 Freescale Semiconductor ...
Страница 4: ...MPC5602P Microcontroller Reference Manual Rev 4 4 Freescale Semiconductor ...
Страница 62: ...Chapter 2 MPC5602P Memory Map MPC5602P Microcontroller Reference Manual Rev 4 62 Freescale Semiconductor ...
Страница 104: ...Chapter 4 Clock Description MPC5602P Microcontroller Reference Manual Rev 4 104 Freescale Semiconductor ...
Страница 128: ...Chapter 6 Power Control Unit MC_PCU MPC5602P Microcontroller Reference Manual Rev 4 128 Freescale Semiconductor ...
Страница 272: ...Chapter 12 e200z0 and e200z0h Core MPC5602P Microcontroller Reference Manual Rev 4 272 Freescale Semiconductor ...
Страница 280: ...Chapter 14 Crossbar Switch XBAR MPC5602P Microcontroller Reference Manual Rev 4 280 Freescale Semiconductor ...
Страница 306: ...Chapter 16 Internal Static RAM SRAM MPC5602P Microcontroller Reference Manual Rev 4 306 Freescale Semiconductor ...
Страница 380: ...Chapter 17 Flash Memory MPC5602P Microcontroller Reference Manual Rev 4 380 Freescale Semiconductor ...
Страница 532: ...Chapter 21 LIN Controller LINFlex MPC5602P Microcontroller Reference Manual Rev 4 532 Freescale Semiconductor ...
Страница 578: ...Chapter 22 FlexCAN MPC5602P Microcontroller Reference Manual Rev 4 578 Freescale Semiconductor ...
Страница 708: ...Chapter 25 FlexPWM MPC5602P Microcontroller Reference Manual Rev 4 708 Freescale Semiconductor ...
Страница 742: ...Chapter 26 eTimer MPC5602P Microcontroller Reference Manual Rev 4 742 Freescale Semiconductor ...
Страница 760: ...Chapter 27 Functional Safety MPC5602P Microcontroller Reference Manual Rev 4 760 Freescale Semiconductor ...
Страница 782: ...Chapter 28 Fault Collection Unit FCU MPC5602P Microcontroller Reference Manual Rev 4 782 Freescale Semiconductor ...
Страница 788: ...Chapter 29 Wakeup Unit WKPU MPC5602P Microcontroller Reference Manual Rev 4 788 Freescale Semiconductor ...
Страница 798: ...Chapter 30 Periodic Interrupt Timer PIT MPC5602P Microcontroller Reference Manual Rev 4 798 Freescale Semiconductor ...
Страница 816: ...Chapter 32 Cyclic Redundancy Check CRC MPC5602P Microcontroller Reference Manual Rev 4 816 Freescale Semiconductor ...
Страница 848: ...Chapter 33 Boot Assist Module BAM MPC5602P Microcontroller Reference Manual Rev 4 848 Freescale Semiconductor ...
Страница 930: ...Chapter 36 Nexus Development Interface NDI MPC5602P Microcontroller Reference Manual Rev 4 930 Freescale Semiconductor ...