5-4
AIC-6915 Ethernet LAN Controller Programmer’s Manual
External Registers
The external registers are used as a standard way to communicate with other modules. All
defined external registers are write-only (from the GFPs point of view). They are used for
providing information to external devices. The following external addresses are defined:
‘0x00’ -
G
FP
S
TATUS
[15:0]
.
‘0x01’ -
G
FP
S
TATUS
[31:16]
.
‘0x02’ - TCP/UDP checksum location
‘0x03’ - TCP/UDP checksum value
‘0x04’ - IP checksum location register
‘0x05’ - IP checksum value register
‘0x06’ - TCP/UDP frame size
‘0x0D - 0x07’ - Reserved
‘0x0E’ - GFP Receive Interrupt.
‘0x0F’ - GFP Transmit Interrupt
16
StopTxDma
- If set, indicates the transmit DMA engine must freeze its operation and
wait for software intervention
17
VlanFrame
- If set, indicates a VLAN 802.1q frame
18
DiscardFrame
- If set, indicates the frame being processed must be discarded (transmit
or receive)
19
PartialChecksumValid
- If set, indicates that Wreg1 stores a valid partial checksum for a
fragmented frame.
20
BypassMaskingIntTimer
- If set, indicates the receive DMA is requested to interrupt the
host immediately after a completion descriptor for current frame is DMA-transferred to
host memory.
21
DmaHeaderOnly
- If set, indicates the receive DMA is requested to the DMA only the
header of the frame being processed. The header size equals 2*(1+GfpFrameCnt[15:0])
bytes at the moment DmaHeaderOnly changes to ‘1’.
22
StartUserData
- When set, this bit indicates that G
FP
F
RAME
C
NT
[15:0]
stores the offset to
the beginning of user data from the start of the Ethernet frame, in 16-bit halfword units.
23
IcmpFrame
- If set, indicates an ICMP frame.
24
SelDescQueue0
- If set, indicates the receive DMA engine is requested to DMA the
frame to buffers specified in Descriptor Queue 0.
25
SelDescQueue1
- If set, indicates the receive DMA engine is requested to DMA the
frame to buffers specified in Descriptor Queue 1.
26
SelCompQueue0
- If set, indicates the receive DMA engine is requested to DMA the
completion descriptor for this frame to queue 0.
27
SelCompQueue1
- If set, indicates the receive DMA engine is requested to DMA the
completion descriptor for this frame to queue 0.
28
Reserved
29
Reserved
30
Reserved
31
Reserved
Table 5-1. Status/Control Register (Continued)
Bit Description