ATM Overview
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
36-7
The following sections describe the transmit and receive mechanisms for the UTOPIA interface. The
expanded cell option is also discussed. Detailed information about UTOPIA mode can be found in
Chapter 42, “Interface Configuration,”
and in
Chapter 43, “UTOPIA Interface.”
36.6.1
UTOPIA Transmit Overview
The UTOPIA transmit process begins with the ATM pace control unit (APC). The APC schedules the ATM
traffic using a scheduling table and a user-configured APC timer (CPM general-purpose timer 4) that
defines the maximum transmit bit rate (bandwidth). The APC maintains the traffic parameters for each
channel and divides the total bandwidth among the active channels. It can provide CBR, VBR and UBR
traffic services. ABR can also be supported through application software manipulation of APC parameters.
See
Chapter 40, “ATM Pace Control,”
for additional information about the operation and programming of
the APC.
With each tick of the APC timer, the APC prepares the channel(s) in the current time slot for transmission
by inserting the channel number(s) into the transmit queue. When the PHY asserts the transmit cell
available (TxClav) signal, the transmitter takes the next channel number from the transmit queue. The
transmitter uses the channel number to find the channel’s transmit connection table (TCT).
For AAL5, the transmitter then copies 48 bytes (or up to 65 bytes for channels configured with expanded
cells) from the external buffer, performs CRC32, copies the cell header from the cell header entry of the
TCT, and sends the complete cell through the UTOPIA interface. For the last cell of an AAL5 frame, the
transmitter appends the trailer of the common part conversion sublayer-protocol data unit (CPCS-PDU) to
the user frame. It pads as required, appends the length (calculated during the frame transmit), and copies
the CPCS-UU and CPI from the TxBD. The transmitter also sets the PTI[1] bit in the header. An interrupt
can be optionally generated to declare the end of the transmit frame.
For AAL0, the transmitter simply copies the cell (except the HEC) prepared by the user from the channel’s
buffer and sends it through the UTOPIA interface. The ATM controller can optionally generate CRC10 on
the cell payload and place the result at the end of the payload (CRC10 field). This feature is used to support
OAM CRC10; refer to the ITU specification I.610 for additional details.
If, however, the current active channel’s buffer is not ready, the transmit process ends and no cell is sent
to the PHY. The PHY is responsible for generating an idle cell in an empty cell slot. An empty cell slot
will continue to be generated each time the APC schedules this channel in the transmit queue until either
a buffer is made ready or a
TRANSMIT DE
ACTIVATE
CHANNEL
command is issued. See
Chapter 39, “ATM
Controller,”
for additional information about ATM controller commands.
Note that the ATM controller does not generate the HEC in UTOPIA mode. The transmitter sends a
dummy byte value (0x00) in place of the HEC; the PHY is responsible for the actual calculation of the
HEC.
36.6.2
UTOPIA Receive Overview
The UTOPIA receive process begins when the PHY asserts the receive cell available signal (RxClav),
indicating that the PHY has a complete cell in its receive FIFO buffer. The ATM controller first receives
the cell header through the UTOPIA interface. The receiver translates the header address
(GFC/VPI/VCI/PTI) to a channel number using either a look-up table in dual-port RAM, address
Содержание PowerQUICC MPC870
Страница 1: ...MPC885 PowerQUICC Family Reference Manual Supports MPC885 MPC880 MPC875 MPC870 MPC885RM Rev 2 04 2006 ...
Страница 98: ...MPC885 PowerQUICC Family Reference Manual Rev 2 I 4 Freescale Semiconductor ...
Страница 118: ...MPC885 Overview MPC885 PowerQUICC Family Reference Manual Rev 2 1 20 Freescale Semiconductor ...
Страница 158: ...The MPC8xx Core MPC885 PowerQUICC Family Reference Manual Rev 2 3 18 Freescale Semiconductor ...
Страница 192: ...MPC885 Instruction Set MPC885 PowerQUICC Family Reference Manual Rev 2 5 22 Freescale Semiconductor ...
Страница 242: ...Instruction and Data Caches MPC885 PowerQUICC Family Reference Manual Rev 2 7 30 Freescale Semiconductor ...
Страница 288: ...MPC885 PowerQUICC Family Reference Manual Rev 2 III 4 Freescale Semiconductor ...
Страница 416: ...External Bus Interface MPC885 PowerQUICC Family Reference Manual Rev 2 13 42 Freescale Semiconductor ...
Страница 440: ...Clocks and Power Control MPC885 PowerQUICC Family Reference Manual Rev 2 14 24 Freescale Semiconductor ...
Страница 554: ...MPC885 PowerQUICC Family Reference Manual Rev 2 V 6 Freescale Semiconductor ...
Страница 606: ...SDMA Channels and IDMA Emulation MPC885 PowerQUICC Family Reference Manual Rev 2 19 20 Freescale Semiconductor ...
Страница 738: ...SCC Asynchronous HDLC Mode and IrDA MPC885 PowerQUICC Family Reference Manual Rev 2 25 16 Freescale Semiconductor ...
Страница 780: ...SCC Ethernet Mode MPC885 PowerQUICC Family Reference Manual Rev 2 27 24 Freescale Semiconductor ...
Страница 794: ...SCC Transparent Mode MPC885 PowerQUICC Family Reference Manual Rev 2 28 14 Freescale Semiconductor ...
Страница 848: ...Serial Peripheral Interface SPI MPC885 PowerQUICC Family Reference Manual Rev 2 30 18 Freescale Semiconductor ...
Страница 882: ...Universal Serial Bus USB MPC885 PowerQUICC Family Reference Manual Rev 2 31 34 Freescale Semiconductor ...
Страница 944: ...Parallel I O Ports MPC885 PowerQUICC Family Reference Manual Rev 2 34 26 Freescale Semiconductor ...
Страница 956: ...CPM Interrupt Controller MPC885 PowerQUICC Family Reference Manual Rev 2 35 12 Freescale Semiconductor ...
Страница 1004: ...Buffer Descriptors and Connection Tables MPC885 PowerQUICC Family Reference Manual Rev 2 37 30 Freescale Semiconductor ...
Страница 1022: ...ATM Parameter RAM MPC885 PowerQUICC Family Reference Manual Rev 2 38 18 Freescale Semiconductor ...
Страница 1068: ...ATM Pace Control MPC885 PowerQUICC Family Reference Manual Rev 2 40 22 Freescale Semiconductor ...
Страница 1090: ...UTOPIA Interface MPC885 PowerQUICC Family Reference Manual Rev 2 43 8 Freescale Semiconductor ...
Страница 1120: ...AAL2 Implementation MPC885 PowerQUICC Family Reference Manual Rev 2 44 30 Freescale Semiconductor ...
Страница 1162: ...Fast Ethernet Controller FEC MPC885 PowerQUICC Family Reference Manual Rev 2 45 40 Freescale Semiconductor ...
Страница 1172: ...SEC Lite Overview MPC885 PowerQUICC Family Reference Manual Rev 2 46 8 Freescale Semiconductor ...
Страница 1176: ...SEC Lite Address Map MPC885 PowerQUICC Family Reference Manual Rev 2 47 4 Freescale Semiconductor ...
Страница 1214: ...SEC Lite Execution Units MPC885 PowerQUICC Family Reference Manual Rev 2 48 38 Freescale Semiconductor ...
Страница 1312: ...Byte Ordering MPC885 PowerQUICC Family Reference Manual Rev 2 A 8 Freescale Semiconductor ...
Страница 1313: ...MPC885 PowerQUICC Family Reference Manual Rev 2 Freescale Semiconductor B 1 Appendix B Serial Communications Performance TBD ...
Страница 1314: ...Serial Communications Performance MPC885 PowerQUICC Family Reference Manual Rev 2 B 2 Freescale Semiconductor ...
Страница 1320: ...Register Quick Reference Guide MPC885 PowerQUICC Family Reference Manual Rev 2 C 6 Freescale Semiconductor ...
Страница 1336: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 16 Freescale Semiconductor ...
Страница 1358: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 38 Freescale Semiconductor ...
Страница 1370: ...MPC880 MPC885 PowerQUICC Family Reference Manual Rev 2 E 4 Freescale Semiconductor ...
Страница 1384: ...Serial ATM Scrambling Reception and SI Programming MPC885 PowerQUICC Family Reference Manual Rev 2 H 6 Freescale Semiconductor ...
Страница 1386: ...Revision History MPC885 PowerQUICC Family Reference Manual Rev 2 I 2 Freescale Semiconductor ...