
Media Local Bus (MLB)
PXN20 Microcontroller Reference Manual, Rev. 1
27-36
Freescale Semiconductor
Figure 27-20. Isochronous/Synchronous Data Buffering Examples
For reception or transmission of isochronous data, single-packet and multi-packet buffering is handled in
the same manner. Since isochronous channels have a fixed packet length (determined by CECR
n
[IPL]),
software should set the system memory buffer length as an even multiple of CECR
n
[IPL] for multi-packet
buffering and equal to CECR
n
[IPL] for single-packet buffering. It is assumed that all isochronous packets
in the system are of the same length, with the minimum supported length being 5 bytes.
For reception or transmission of synchronous data, the concept of multi-packet or single-packet buffering
is not applicable since synchronous data has no packet format. As a result, CCBCR
n
[BFA] always
indicates the end address of the
Current Buffer
for synchronous channels.
27.4.7
DMA Controller (Circular Buffering)
Logical channels can be programmed to operate using circular buffering by programming
CECR
n
[MDS[1:0]] = 01. It is recommended that circular buffering be used with synchronous channels
only (CECR
n
[CT[1:0]] = 00). Logical channels configured for transmitting or receiving other types of
data (e.g. asynchronous, control, or isochronous) should not use circular buffering.
In contrast ping-pong buffering, this mode effectively uses a single, circular system memory buffer to
process channel data. Software must program the beginning and ending address of the circular buffer in
the CNBCR
n
[BSA] and CNBCR
n
[BEA] fields. For proper operation, software must not change the
addresses in CNBCR
n
[BSA] and CNBCR
n
[BEA] once buffer processing has started.
Isochronous
BS
BD
BCA
BFA
BEA
BSA
BCA
Note 3
Note 1
Note 4
Note 2
Legend
= 16-bit address pointer
= channel interrupt
(Shows RX/TX handling of Isochronous/Synchronous Data using the Current Buffer)
Isochronous/Synchronous Data Buffering Examples
(First Packet)
Packet 1
Isochronous
Packet 2
Isochronous
Packet 3
Isochronous
(Last Packet)
Packet N
Synchronous
Data
Current Buffer
for Synchronous
channel
Current Buffer
for Isochronous
channel
Содержание PXN2020
Страница 1: ...PXN20 Microcontroller Reference Manual Devices Supported PXN2020 PXN2120 PXN20RM Rev 1 06 2011...
Страница 42: ...PXN20 Microcontroller Reference Manual Rev 1 lxiv Freescale Semiconductor...
Страница 64: ...Introduction PXN20 Microcontroller Reference Manual Rev 1 1 22 Freescale Semiconductor...
Страница 112: ...Signal Description PXN20 Microcontroller Reference Manual Rev 1 3 44 Freescale Semiconductor...
Страница 118: ...Resets PXN20 Microcontroller Reference Manual Rev 1 4 6 Freescale Semiconductor...
Страница 162: ...Clocks Reset and Power CRP PXN20 Microcontroller Reference Manual Rev 1 6 30 Freescale Semiconductor...
Страница 182: ...Frequency Modulated Phase Locked Loop FMPLL PXN20 Microcontroller Reference Manual Rev 1 7 20 Freescale Semiconductor...
Страница 268: ...Boot Assist Module BAM PXN20 Microcontroller Reference Manual Rev 1 9 14 Freescale Semiconductor...
Страница 318: ...Interrupts and Interrupt Controller INTC PXN20 Microcontroller Reference Manual Rev 1 10 50 Freescale Semiconductor...
Страница 326: ...General Purpose Static RAM SRAM PXN20 Microcontroller Reference Manual Rev 1 11 8 Freescale Semiconductor...
Страница 372: ...e200z6 Core Z6 PXN20 Microcontroller Reference Manual Rev 1 13 8 Freescale Semiconductor...
Страница 412: ...e200z0 Core Z0 PXN20 Microcontroller Reference Manual Rev 1 14 14 Freescale Semiconductor...
Страница 460: ...Memory Protection Unit MPU PXN20 Microcontroller Reference Manual Rev 1 18 20 Freescale Semiconductor...
Страница 478: ...Error Correction Status Module ECSM PXN20 Microcontroller Reference Manual Rev 1 19 18 Freescale Semiconductor...
Страница 488: ...Software Watchdog Timer SWT PXN20 Microcontroller Reference Manual Rev 1 20 10 Freescale Semiconductor...
Страница 494: ...System Timer Module STM PXN20 Microcontroller Reference Manual Rev 1 21 6 Freescale Semiconductor...
Страница 821: ...Media Local Bus MLB PXN20 Microcontroller Reference Manual Rev 1 Freescale Semiconductor 27 49...
Страница 822: ...Media Local Bus MLB PXN20 Microcontroller Reference Manual Rev 1 27 50 Freescale Semiconductor...
Страница 926: ...Controller Area Network FlexCAN PXN20 Microcontroller Reference Manual Rev 1 29 42 Freescale Semiconductor...
Страница 990: ...Deserial Serial Peripheral Interface DSPI PXN20 Microcontroller Reference Manual Rev 1 30 64 Freescale Semiconductor...
Страница 1044: ...Enhanced Serial Communication Interface eSCI PXN20 Microcontroller Reference Manual Rev 1 31 54 Freescale Semiconductor...
Страница 1080: ...Cross Triggering Unit CTU PXN20 Microcontroller Reference Manual Rev 1 33 12 Freescale Semiconductor...
Страница 1134: ...Analog to Digital Converter ADC PXN20 Microcontroller Reference Manual Rev 1 34 54 Freescale Semiconductor...
Страница 1150: ...IEEE 1149 1 Test Access Port Controller JTAGC PXN20 Microcontroller Reference Manual Rev 1 35 16 Freescale Semiconductor...
Страница 1257: ...Nexus Development Interface NDI PXN20 Microcontroller Reference Manual Rev 1 Freescale Semiconductor 36 107...
Страница 1258: ...Nexus Development Interface NDI PXN20 Microcontroller Reference Manual Rev 1 36 108 Freescale Semiconductor...
Страница 1376: ...Memory Map PXN20 Microcontroller Reference Manual Rev 1 A 118 Freescale Semiconductor...