
IDT Ethernet Interfaces
DMA Interface
79RC32438 User Reference Manual
11 - 12
November 4, 2002
Notes
Ethernet Station Address [0|1|2|3] High Register
Figure 11.9 Ethernet Station Address [0|1|2|3] High Register (ETH[0|1]SAH[0|1|2|3])
DMA Interface
An Ethernet interface supports DMA operations from the input FIFO to memory, and DMA operations
from memory to the output FIFO (See Chapter 9, DMA Controller). Ethernet DMA operations do not use the
DMA descriptor device command (DEVCMD) field.
Ethernet Input DMA Operations
Table 11.2 summarizes Ethernet interface input DMA operations. As shown in Figure 11.10, the DMA
descriptor device control and status (DEVCS) field is used to record status information for received packets.
A DMA request event is generated whenever 16 full FIFO data words exist in the input FIFO or when a
FIFO data word tagged as an end-of-packet is present in the input FIFO. This causes the DMA to transfer
data from the input FIFO to memory.
Read Value:
Previous value written
Write Effect:
Modify value
BYTE2
Description:
Byte Two.
This field contains byte Two of the 48-bit MAC address. For example, for the MAC
address AC-DE-48-00-00-80, this field holds the value 48.
Initial Value:
Undefined
Read Value:
Previous value written
Write Effect:
Modify value
BYTE1
Description:
Byte One.
This field contains byte one of the 48-bit MAC address. For example, for the MAC
address AC-DE-48-00-00-80, this field holds the value DE.
Initial Value:
Undefined
Read Value:
Previous value written
Write Effect:
Modify value
BYTE0
Description:
Byte Zero.
This field contains byte zero of the 48-bit MAC address. For example, for the MAC
address AC-DE-48-00-00-80, this field holds the value AC.
Initial Value:
Undefined
Read Value:
Previous value written
Write Effect:
Modify value
ETH[0|1]SAH[0|1|2|3]
0
31
16
0
8
BYTE0
8
BYTE1