Non-PCI Single-Chip Full Duplex Ethernet Controller with Magic Packet
The COUNTER REGISTER facilitates maintaining statistics in the AUTO RELEASE mode where no
transmit interrupts are generated on successful transmissions.
Reading the register in the transmit service routine will be enough to maintain statistics.
I/O SPACE - BANK0
OFFSET
8
NAME
TYPE
READ ONLY
SYMBOL
MIR
MEMORY INFORMATION REGISTER
For software compatibility with other LAN9000 parts all memory-related information is represented in 256 x
M byte units, where the multiplier M is determined by the MCR upper byte. M equals “1” for the
LAN91C96.
FREE MEMORY AVAILABLE (in BYTES* 256* M)
0
0
0
0
0
1
1
0
0
0
0
0
MEMORY SIZE (in BYTES* 256* M)
0
1
1
0
FREE MEMORY AVAILABLE - This register can be read at any time to determine the amount of free
memory. The register defaults to the MEMORY SIZE upon reset or upon the RESET MMU command.
MEMORY SIZE - This register can be read to determine the total memory size, and will always read 18H
(6144 bytes) for the LAN91C96.
MEMORY SIZE REGISTER
M
1
1
ACTUAL MEMORY
64 kbytes
LAN91C90
LAN91C90
LAN91C92/
LAN91C94
LAN91C95
LAN91C96
LAN91C100
FFH
40H
12H
16 kbytes
4608 bytes
1
18H
18H
FFH
1
1
2
6144 bytes
6144 bytes
128 kbytes
I/O SPACE - BANK0
OFFSET
NAME
TYPE
SYMBOL
MCR
LOWER BYTE READ/WRITE
UPPER BYTE READ ONLY
MEMORY CONFIGURATION
A
REGISTER
Memory Size Multiplier “M”
0
0
0
0
1
1
0
0
1
1
0
Memory Reserved for Transmit (in BYTES * 256 * M)
0
0
0
0
0
MEMORY RESERVED FOR TRANSMIT -
Programming this value allows the host CPU to reserve memory to be used later for transmit, limiting the
amount of memory that receive packets can use up. When programmed for zero, the memory allocation
between transmit and receive is completely dynamic. When programmed for a non-zero value, the
allocation is dynamic if the free memory exceeds the programmed value, while receive allocation requests
are denied if the free memory is less or equal to the programmed value. This register defaults to zero
upon reset. It is not affected by the RESET MMU command.
The value written to the MCR is a reserved memory space IN ADDITION TO ANY MEMORY
CURRENTLY IN USE. If the memory allocated for transmit plus the reserved space for transmit is required
SMSC LAN91C965v&3v
Page 47
Rev. 09/10/2004
DATASHEET
SMSC [ SMSC CORPORATION ]
