![Freescale Semiconductor MPC8250 Скачать руководство пользователя страница 935](http://html1.mh-extra.com/html/freescale-semiconductor/mpc8250/mpc8250_family-reference-manual_2330549935.webp)
ATM Controller and AAL0, AAL1, and AAL5
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
Freescale Semiconductor
30-15
30.4.2
Address Compression
The address compression mechanism uses two levels of address translation to help minimize the memory
space needed to cover the available address range. The first level of translation (VP-level) uses a look-up
table based on the 4-bit PHY address and the 12-bit virtual path identifier; the second level (VC-level) uses
the 16-bit virtual channel identifier. If there is no match during address compression, the cell is considered
a misinserted cell.
During the VP-level translation, VP_MASK in the ATM parameter RAM compresses an incoming cell’s
PHY address and VPI to create an index into the VP-level table. The VP-level table entry consists of
another mask (VC_MASK) and a pointer to one of the VC-level tables (VCOFFSET). Note that the VP
table should reside in the dual-port RAM.
In the VC-level translation, the VCI is compressed with the VC_MASK to generate a pointer to the
VC-level table entry containing the received cell’s channel code. The VC table should reside in external
memory.
Figure 30-5
shows an example of address compression.
Figure 30-5. Address Compression Mechanism
Figure 30-5
shows VP_MASK selecting five VPI bits to index the VP-level table. The VP-level table entry
contains the 16-bit mask (VC_MASK) and the VC-level table offset (VCOFFSET) for the next level of
address mapping. The VC_MASK selects VCI bits 4–10, which is used with VCT_BASE and VCOFFSET
32-bit entries
VP-level addressing table
VPI
0000
00011111
VPpointer
VPT_BASE
VCOFFSET
VC_MASK
VCI
00000111 11110000
VCpointer
32-bit entries
VC-level addressing tables
VCT_BASE
VP_MASK
16 bit
16 bit
PHY Addr
0000
16 bit
12 bit
4 bit
(in external memory)
(in dual-port RAM recommended)
Ch Code[15–0]
—
16 bit
15 bit
MS
1 bit
31
0
31
0
0b00011
Содержание MPC8250
Страница 90: ...MPC8260 PowerQUICC II Family Reference Manual Rev 2 lxxxviii Freescale Semiconductor...
Страница 94: ...MPC8260 PowerQUICC II Family Reference Manual Rev 2 I 4 Freescale Semiconductor...
Страница 118: ...Overview MPC8260 PowerQUICC II Family Reference Manual Rev 2 1 24 Freescale Semiconductor...
Страница 236: ...Reset MPC8260 PowerQUICC II Family Reference Manual Rev 2 5 14 Freescale Semiconductor...
Страница 274: ...60x Signals MPC8260 PowerQUICC II Family Reference Manual Rev 2 7 18 Freescale Semiconductor...
Страница 540: ...IEEE 1149 1 Test Access Port MPC8260 PowerQUICC II Family Reference Manual Rev 2 13 8 Freescale Semiconductor...
Страница 548: ...MPC8260 PowerQUICC II Family Reference Manual Rev 2 IV 8 Freescale Semiconductor...
Страница 704: ...Serial Communications Controllers SCCs MPC8260 PowerQUICC II Family Reference Manual Rev 2 20 26 Freescale Semiconductor...
Страница 770: ...SCC BISYNC Mode MPC8260 PowerQUICC II Family Reference Manual Rev 2 23 20 Freescale Semiconductor...
Страница 808: ...SCC Ethernet Mode MPC8260 PowerQUICC II Family Reference Manual Rev 2 25 24 Freescale Semiconductor...
Страница 848: ...Serial Management Controllers SMCs MPC8260 PowerQUICC II Family Reference Manual Rev 2 27 36 Freescale Semiconductor...
Страница 972: ...ATM Controller and AAL0 AAL1 and AAL5 MPC8260 PowerQUICC II Family Reference Manual Rev 2 30 52 Freescale Semiconductor...
Страница 1062: ...ATM AAL1 Circuit Emulation Service MPC8260 PowerQUICC II Family Reference Manual Rev 2 31 46 Freescale Semiconductor...
Страница 1072: ...ATM AAL2 MPC8260 PowerQUICC II Family Reference Manual Rev 2 32 10 Freescale Semiconductor...
Страница 1122: ...Inverse Multiplexing for ATM IMA MPC8260 PowerQUICC II Family Reference Manual Rev 2 33 20 Freescale Semiconductor...
Страница 1178: ...Inverse Multiplexing for ATM IMA MPC8260 PowerQUICC II Family Reference Manual Rev 2 33 76 Freescale Semiconductor...
Страница 1224: ...Fast Ethernet Controller MPC8260 PowerQUICC II Family Reference Manual Rev 2 35 28 Freescale Semiconductor...
Страница 1242: ...FCC HDLC Controller MPC8260 PowerQUICC II Family Reference Manual Rev 2 36 18 Freescale Semiconductor...
Страница 1302: ...Register Quick Reference Guide MPC8260 PowerQUICC II Family Reference Manual Rev 2 A 4 Freescale Semiconductor...
Страница 1318: ...Reference Manual Rev 1 Errata MPC8260 PowerQUICC II Family Reference Manual Rev 2 B 16 Freescale Semiconductor...
Страница 1356: ...MPC8260 PowerQUICC II Family Reference Manual Rev 2 Index 28 Freescale Semiconductor U U Index...