Motorola MPC8260 - Manual (Page 677)

MOTOROLA Chapter 24. SCC Ethernet Mode 24-9
Part IV. Communications Processor Module
0x54 MAX_B Hword Maximum BD byte count.
0x58 GADDR1 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
SET GROUP
ADDRESS command is used to enable the hash table.
0x5A GADDR2
0x5C GADDR3
0x5E GADDR4
0x60 TBUF0_DATA0 Word Save area 0Ñcurrent frame.
0x64 TBUF0_DATA1 Word Save area 1Ñcurrent frame.
0x68 TBUF0_RBA0 Word
0x6C TBUF0_CRC Word
0x70 TBUF0_BCNT Hword
0x72 PADDR1_H 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.
0x74 PADDR1_M
0x76 PADDR1_L
0x78 P_PER 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.
0x7A RFBD_PTR Hword Rx Þrst BD pointer.
0x7C TFBD_PTR Hword Tx Þrst BD pointer.
0x7E TLBD_PTR Hword Tx last BD pointer.
0x80 TBUF1_DATA0 Word Save area 0Ñnext frame.
0x84 TBUF1_DATA1 Word Save area 1Ñnext frame.
0x88 TBUF1_RBA0 Word
0x8C TBUF1_CRC Word
0x90 TBUF1_BCNT Hword
0x92 TX_LEN Hword Tx frame length counter.
0x94 IADDR1 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 command is used to enable the hash table.
0x96 IADDR2
0x98 IADDR3
0x9A IADDR4
0x9C BOFF_CNT Hword Backoff counter.
Table 24-1. SCC Ethernet Parameter RAM Memory Map (Continued)
Offset 1 Name Width Description