MB86960 Datasheet, PDF (13/65 Pages) Fujitsu Component Limited. – NETWORK INTERFACE CONTROLLER with ENCODER/DECODER (NICE)

MB86960
TRANSMIT
BUFFERS
ONE OR TWO
TRANSMIT BUFFERS
T
RECEIVED
PACKET
n+3
(LAST PART)
CURRENTLY
AVAILABLE
FREE BUFFER
AREA
RECEIVED
PACKET n
RECEIVED
PACKET n + 1
RECEIVE
BUFFER
RING
62 KBYTES
MAX
RECEIVED
PACKET n + 2
RECEIVED
PACKET n + 3
(FIRST PART)
L
NOTES
1. Length (L) = 8, 16, 32, or 64 Kbytes.
2. Transmit Size (T) = 2 (one bank), 4 (two banks), 8
(two banks), or 16 (two banks) Kbytes.
3. Receive packets are aligned on an eight byte
boundary
.
4. Each received packet is preceded by a four byte
packet header as follows:
Byte 0 – Packet Status
Byte 1 – Not Used
Byte 2 – Packet Size LSB’s
Byte 3 – Packet Size MSB’s
Figure 5. Buffer Memory Organization
As shown in the buffer memory is divided into transmit
and receive buffer areas. The partitioning of the memory
is programmable, allowing the system to be configured
with different proportions of space available for the
transmitter and receiver functions. By programming the
proportions, an optimum usage of the memory can be
selected, according to the demands of a particular
application.
The section of the memory used by the transmitter can be
configured as a single buffer 2 kilobytes long, or as a pair
of banks, each either 2, 4 or 8 kilobytes long. Within each
buffer or bank, one or more packets can be written by the
system until the available space is too small for another
packet. Once started, the transmitter will transmit all
packets in the buffer automatically before finishing with a
status update, and an interrupt if so enabled. With the
two-bank configurations, one bank can be transmitted
while the other is being loaded. Using dual buffers and
loading multiple packets for “packet chaining” gives the
highest rate of transmission. This will boost performance
for systems that require high throughput transmission.
NICE can be configured to operate with 8, 16, 32 or 64
kilobytes of total buffer memory size, including both
transmit and receive spaces. This memory partitioning
into transmit and receive sections is allocated by the
system software. The total size of the transmit buffer
space can be either 2, 4, 8 or 16 kilobytes. Immediately
following the transmit buffer space is the receive buffer
space, using the balance of the available memory.