MPC8280 datasheet(1052/1386 Pages) FREESCALE

1052 / 1386 page

ATM Controller and AAL0, AAL1, and AAL5

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

31-92

Freescale Semiconductor

Table 31-50 describes FTIRRx fields.

Figure 31-63 shows how transmit clocks are determined.

Figure 31-63. FCC Transmit Internal Rate Clocking

31.15.1.2 Example

Suppose the MPC8280 is connected to four 155 Mbps PHY devices and the maximum transmission rate

is 155 Mbps for the first PHY and 10 Mbps for the rest of the PHYs. The BRG CLK should be set

according to the highest rate. If the CPM clock is 133 MHz and the BRG CLK is 66 MHz, the BRG should

be programmed to divide the CPM clock by 181 to generate cell transmit requests every 362 system clocks:

Field

TRM

Initial Value

Reset

0000_0000

R/W

Address

GFEMR[TIREM=0]

FCC1: 0x1131C (FTIRR1_PHY0),

FCC1: 0x1131D (FTIRR1_PHY1),

FCC1: 0x1131E (FTIRR1_PHY2),

FCC1: 0x1131F (FTIRR1_PHY3),

FCC2: 0x1133C (FTIRR2_PHY0),

FCC2: 0x1133D (FTIRR2_PHY1),

FCC2: 0x1133E (FTIRR2_PHY2),

FCC2: 0x1133F (FTIRR2_PHY3).

GFEMR[TIREM=1]

FCC1: 0x1131C (FTIRR1_GRP0),

FCC1: 0x1131D (FTIRR1_GRP1),

FCC1: 0x1131E (FTIRR1_GRP2),

FCC1: 0x1131F (FTIRR1_GRP3),

FCC2: 0x1133C (FTIRR2_GRP0),

FCC2: 0x1133D (FTIRR2_GRP1),

FCC2: 0x1133E (FTIRR2_GRP2),

FCC2: 0x1133F (FTIRR2_GRP3).

Figure 31-62. FCC Transmit Internal Rate Register (FTIRR)

Table 31-50. FTIRR

x Field Descriptions

Bit

Name

Description

0TRM

(TIREM=0)

PHY transmit mode

0 External rate mode.

1 Internal rate mode.

TRM

(TIREM=1)

Group transmit mode

Group rate timer [x] disabled.

1 Internal rate timer for Group[x] is enabled and division factor is set by Initial Value field.

1–7

Initial Value

The initial value of the internal rate timer. A value of 0x7F produces the minimum clock rate

(BRG CLK divided by 128); 0x00 produces the maximum clock rate (BRG CLK divided by 1).

BRG CLK

PHY#0 Int rate timer

PHY#1 Int rate timer

PHY#2 Int rate timer

PHY#3 Int rate timer

PHY# 0 or GRP#0 Tx Rate

PHY# 1 or GRP#1Tx Rate

PHY# 2 or GRP#2 Tx Rate

PHY# 3 or GRP#3 Tx Rate

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