CS8900-CQ3 Cirrus Logic, CS8900-CQ3 Datasheet - Page 76

• Manufacturer Part Number: CS8900-CQ3
• Description: Crystal LAN ISA Ethernet Controller
• Manufacturer: Cirrus Logic

1) A frame is received by the CS8900A, triggering
2) The host reads the Interrupt Status Queue
3) The host reads RxStatus (memory base +
4) The host reads RxLength (memory base +
5) The host reads the frame data by executing re-
For a more detailed description of receive, see
Section 5.2 on page 79.
4.9.5 Polling the CS8900A in Memory Mode
If interrupts are not used, the host can poll the
CS8900A to check if receive frames are present
and if memory space is available for transmit.
However, this is beyond the scope of this data
sheet.
4.10 I/O Space Operation
In I/O Mode, PacketPage memory is accessed
through eight 16-bit I/O ports that are mapped into
16 contiguous I/O locations in the host system’s I/O
space. I/O Mode is the default configuration for the
CS8900A and is always enabled. On power up, the
default value of the I/O base address is set at 300h.
(Note that 300h is typically assigned to LAN pe-
ripherals). The I/O base address may be changed to
any available XXX0h location, either by loading
configuration data from the EEPROM, or during
system setup. Table 17 shows the CS8900A I/O
Mode mapping.
76
Offset
0000h Read/Write Receive/Transmit Data (Port 0)
0002h Read/Write Receive/Transmit Data (Port 1)
an enabled interrupt.
(memory base + 0120h) and is informed of the
receive frame.
0400h) to learn the status of the receive frame.
0402h) to learn the frame’s length.
petitive memory-to-memory move instructions
(REP MOVS) from memory base + 0404h to
transfer the entire frame from CS8900A mem-
ory to host memory.
Type
Table 17. I/O Mode Mapping
Description
CIRRUS LOGIC PRODUCT DATA SHEET
4.10.1 Receive/Transmit Data Ports 0 and 1
These two ports are used when transferring trans-
mit data to the CS8900A and receive data from the
CS8900A. Port 0 is used for 16-bit operations and
Ports 0 and 1 are used for 32-bit operations (lower-
order word in Port 0).
4.10.2 TxCMD Port
The host writes the Transmit Command (TxCMD)
to this port at the start of each transmit operation.
The Transmit Command tells the CS8900A that the
host has a frame to be transmitted, as well as how
that frame should be transmitted. This port is
mapped into PacketPage base + 0144h. See Regis-
ter 9 in Section 4.4 on page 47 for more informa-
tion.
4.10.3 TxLength Port
The length of the frame to be transmitted is written
here immediately after the Transmit Command is
written. This port is mapped into PacketPage base
+ 0146h.
4.10.4 Interrupt Status Queue Port
This port contains the current value of the Interrupt
Status Queue (ISQ). The ISQ is located at Pack-
etPage base + 0120h. For a more detailed descrip-
tion of the ISQ, see Section 5.1 on page 79.
4.10.5 PacketPage Pointer Port
The PacketPage Pointer Port is written whenever
the host wishes to access any of the CS8900A’s in-
ternal registers. The first 12 bits (bits 0 through B)
provide the internal address of the target register to
be accessed during the current operation. The next
000Ch Read/Write
Offset
000Ah Read/Write
000Eh Read/Write
0004h
0006h
0008h
Crystal LAN™ ISA Ethernet Controller
Read-only
Write-only
Write-only
Type
Table 17. I/O Mode Mapping
TxCMD (Transmit Command)
TxLength (Transmit Length)
PacketPage Data (Port 0)
PacketPage Data (Port 1)
Interrupt Status Queue
PacketPage Pointer
Description
CS8900A
DS271PP3