15
The MMnet102_BANKSR register contained under the address 0xFF00 is used for the choice of an active
RAM memory bank. The contents of this register have a meaning only when mode 1 of the memory controller
is chosen. The register has only four lowest bits, during readout the remaining bits (4 – 7) have the value „0”
and the value written into them has no meaning.
MMnet102_BANKSR 0xFF00
-
-
-
-
BANKSR3
BANKSR2
BANKSR1
BANKSR0
7
6
5
4
3
2
1
0
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Under the address 0xFF01 is the configuration register of the memory controller. Through this register the
operating mode of the controller and the SEL output can be chosen. Configuration should be set after every
system reset.
MMnet102_CONF
0xFF01
SEL2POL
SEL2CFG1 SEL2CFG0
SEL1POL
SEL1CFG1 SEL1CFG0
MODE1
MODE0
7
6
5
4
3
2
1
0
W
W
W
W
W
W
W
W
The meaning of individual bits in the MMnet102_CONF register is shown by the table below:
No.
Name
Description
7
SEL2POL SEL2 output polarization. „0” – active low level
6
5
SEL2CFG1
SEL2CFG0 Operating mode of SEL2 output
4
SEL1POL SEL1 output polarization. „0” – active low level
3
2
SEL1CFG1
SEL1CFG0 Operating mode of SEL1 output.
1
0
MODE1
MODE0
Operating mode of the address decoder.
This register is assigned only for writing. An attempt of readout will return only random values.
Two lowest bits of the MMnet102_CONF register, assigned as MODE1 and MODE2, serve to set the
operating mode of the address decoder:
Mode
MODE1..0
Description
0
00
Conformity mode with earlier equipment and software versions.
Available is only 32kB of RAM memory located in the lower area of the
address space, and the Ethernet controller under the addresses 0x8000-
0x9000.
1
01
Memory banking mode.
32kB of non-banking memory is available; the
remaining memory is accessible in banks of 16kB each. The Ethernet
controller is under the address 0xC000.
2
10
Mode of maximum linear memory.
In this mode the user has at his
disposal 65280 memory bites without the need to serve banking. The
LAN91C111 controller is under the address 0xFF80.
