Motorola MPC8260 PowerQUICC II User Manual page 677

Table 24-1. SCC Ethernet Parameter RAM Memory Map (Continued)
1
Offset Name
0x54 MAX_B
0x58 GADDR1
0x5A GADDR2
0x5C GADDR3
0x5E GADDR4
0x60 TBUF0_DATA0 Word
0x64 TBUF0_DATA1 Word
0x68 TBUF0_RBA0 Word
0x6C TBUF0_CRC
0x70 TBUF0_BCNT Hword
0x72 PADDR1_H
0x74 PADDR1_M
0x76 PADDR1_L
0x78 P_PER
0x7A RFBD_PTR
0x7C TFBD_PTR
0x7E TLBD_PTR
0x80 TBUF1_DATA0 Word
0x84 TBUF1_DATA1 Word
0x88 TBUF1_RBA0 Word
0x8C TBUF1_CRC
0x90 TBUF1_BCNT Hword
0x92 TX_LEN
0x94 IADDR1
0x96 IADDR2
0x98 IADDR3
0x9A IADDR4
0x9C BOFF_CNT
MOTOROLA
Width
Hword Maximum BD byte count.
Hword Group address Þlter 1Ð4. Used in the hash table function of the group addressing
mode. Write zeros to these values after reset and before the Ethernet channel is
enabled to disable all group hash address recognition functions. The
command is used to enable the hash table.
ADDRESS
Save area 0Ñcurrent frame.
Save area 1Ñcurrent frame.
Word
Hword The 48-bit individual address of this station into this location. PADDR1_L is the
lowest order hword and PADDR1_H is the highest order hword.
Hword Persistence. Lets the Ethernet controller be less aggressive after a collision.
Normally, 0x0000. It can be a value between 1 and 9 (1 is most aggressive). The
value is added to the retry count in the backoff algorithm to reduce the chance of
transmission on the next time slot.
Note: Using P_PER is fully allowed in the Ethernet/802.3 specifications. A less
aggressive backoff algorithm used by multiple stations on a congested Ethernet
LAN increases overall throughput by reducing the chance of collision. PSMR[SBT]
offers another way to reduce the aggressiveness of the Ethernet controller.
Hword Rx Þrst BD pointer.
Hword Tx Þrst BD pointer.
Hword Tx last BD pointer.
Save area 0Ñnext frame.
Save area 1Ñnext frame.
Word
Hword Tx frame length counter.
Hword Individual address Þlter 1Ð4. Used in the hash table function of the individual
addressing mode. Zeros can be written to these values after reset and before the
Ethernet channel is enabled to disable all individual hash address recognition
functions. The
SET GROUP ADDRESS
Hword Backoff counter.
Chapter 24. SCC Ethernet Mode
Part IV. Communications Processor Module
Description
command is used to enable the hash table.
SET GROUP
24-9