MPC8280 datasheet(976/1386 Pages) FREESCALE

976 / 1386 page

ATM Controller and AAL0, AAL1, and AAL5

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

31-16

Freescale Semiconductor

to indicate the received cell’s channel code. Address compression field descriptions are shown in

Table 31-3.

31.4.2.1

VP-Level Address Compression Table (VPLT)

The size of the VP-level table depends on the number of mask bits in VP_MASK. For example, if only

one PHY is available (PHY address = 0) and VPMASK = 0b11_1111_1111, VP pointer contains ten bits

and the table is 4 Kbytes. Because each VPLT entry is 4 bytes, the address of an entry is VPT_BASE + VP

pointer

× 4.

Each VPLT entry has two parameters:

•

VC_MASK—A 16-bit VC-level mask for masking the incoming cell’s VCI

•

VCOFFSET—A 16-bit VC-level table offset from VC_BASE that points to the appropriate

VC-level table’s (VCLT) starting address. The address of the VCLT is VC_BASE + VCOFFSET

× 4.

If the VCLTs are to be placed contiguously in memory, each table’s VCOFFSET depends on the

size of preceding tables. Each table’s size depends on the number of ones in VC_MASK.

Figure 31-6 gives the general formula for determining VCOFFSET.

Table 31-4 shows example VCOFFSET calculations for a VP-level table with four entries.

Table 31-3. Field Descriptions for Address Compression

Field

Description

PHY

Addr

In multiple PHY mode, this field contains the 4 least-significant bits of the current channel’s physical

address. Because this comparison field is limited to 4 bits, two sets of look-up tables are needed if using

more than 16 PHYs.The msb of the PHY address (bit 4) selects between the two sets of tables. If the msb

is zero, the CP accesses the tables at VPT_BASE and VCT_BASE; if the msb is set, the CP uses

VPT1_BASE and VCT1_BASE. See Section 16.4.1, “CMX UTOPIA Address Register (CMXUAR).”

In single PHY mode, clear this field.

VCI, VPI The VCI and VPI of the current channel.

Ch Code Pointer to internal or external connection table.

—

Reserved, should be cleared.

Match status.

0 Match was found.

1 Match was not found.

General formula: VCOFFSET(n+1) = VCOFFSETn + 2

(number of ones in VC_MASKn)

Figure 31-6. General VCOFFSET Formula for Contiguous VCLTs

Table 31-4. VCOFFSET Calculation Examples for Contiguous VCLTs

VP-Level

Table Entry

VC_MASK

Number of Ones

in VC_MASK

VC-Level

Table Size

VCOFFSET

0x0237

26 = 64 entries

0x0230

23 = 8 entries

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