cs89712 Cirrus Logic, Inc., cs89712 Datasheet - Page 72

• Manufacturer Part Number: cs89712
• Description: High-performance, Low-power System-on-chip With 10base-t Ethernet Controller
• Manufacturer: Cirrus Logic, Inc.

3.2.1
This section refers to the eight 2-byte registers re-
siding in the 16-byte window at 0x2000.3000.
These registers are always immediately available.
3.2.1.1
These two ports are used when transferring trans-
mitting/receving data to/from the CS89712. Port 0
is used for 16-bit operations and Ports 0 and 1 are
for 32-bit operations (lower-order word in Port 0).
3.2.1.2
Software writes the Transmit Command (TxCMD)
to this port at the start of each transmit operation.
The Transmit Command indicates that the software
has a frame to be transmitted, as well as how that
frame should be transmitted. See Section 3.2.3,
“Ethernet Status/Control Registers” for more in-
formation.
3.2.1.3
The length of the frame to be transmitted is written
here immediately after the Transmit Command is
written.
72
Ethernet Port Register Window
Receive/Transmit Data Ports 0 & 1
TxCMD Port
TxLength Port
F E
D C
base + 000Bh
Bit F: 0 = Pointer remains fixed
Figure 22. Ethernet Port Pointer
B A
1 = Auto-Increments to next word location
9 8
Register Address
7 6
3.2.1.4
This port contains the current value of the Interrupt
Status Queue (ISQ). For a more detailed descrip-
tion of the ISQ, see Section 2.31, “Managing Inter-
rupts & Status Queue”.
3.2.1.5
The Ethernet Port Pointer is written in order to ac-
cess any of the Ethernet port indexed registers
(which reside in the 4 Kbyte memory page). The
first 12 bits (bits 0 through B) of the pointer provide
the offset of the target register to be accessed dur-
ing the current operation. The next three bits (C, D,
and E) are read-only and will always read as 011b.
Any convenient value may be written to these bits
when writing to the Ethernet Port Pointer Port. The
last bit (Bit F) indicates whether or not the Ethernet
Port Pointer should be auto-incremented to the next
word location.
Ethernet Port Pointer.
3.2.1.6
The Ethernet Port Data Ports are used to transfer
data to and from any of the CS89712’s internal reg-
isters. Port 0 is used for 16-bit operations and Port
0 and 1 are used for 32-bit operations (lower-order
word in Port 0).
5 4
base + 000Ah
3 2
Interrupt Status Queue Port
Ethernet Port Pointer
Ethernet Port Data Ports 0 and 1
Figure 22
1 0
shows the structure of the
CS89712
DS502PP2