System Configuration Jumper; Timing Specifications - 3Com EtherLink/MC Technical Reference Manual

EtherLink/MC:
2
Functional Description
2-5
System Configuration Jumper
There is a single jumper on EtherLink/MC adapter. This jumper is used to allow the adapter to be
enabled even though the host system's Configuration RAM contains no entry for the adapter. There
is only one condition under which the adapter's jumper should be moved from position "A" to
position "B": if the adapter has been installed in a computer that has no floppy disk drives and there
as no provision for temporarily installing one to run the configuration utility on the system's
reference diskette.
When the jumper is installed in position "B", the Card Enable feature of POS is overridden so that
the adapter's Start ROM program can be accessed during the ROM scan that occurs during the
power-up sequence. This Card Enable override is necessary when the host system's configuration
RAM doesn't contain an entry for the adapter. Without the jumper, if there isn't an entry in the
system's CMOS RAM for the adapter, the system will leave the adapter in the disabled state and its
ROM won't be found during the ROM scan.
When using the adapter in this specialized configuration, care must be taken that no bus conflicts
will occur because the adapter will be enabled before it is configured. The power-up default
configuration for the adapter is as follows: I/O base address = 0300H, memory base address =
0C0000H, interrupt level = 12 and the on-board transceiver will be selected.
For general operation, the jumper should be in position "A".
Timing Specifications
Micro Channel to/from Packet Buffer
o Basic memory cycle time: 300 nanoseconds
82586 to/from Packet Buffer
® Network bit rate: 10.00 Mb/s
, Network data word transfer rate: 1.6 microseconds/word
o Compressed 82586 bus cycle time: 333.3 nanoseconds
~ Adapter bus bandwidth consumption: 21%
82586 FIFO empty/fill rate
• Maximum 82586 burst transfer rate: 24 Mbps
Maximum Packet Buffer Access Latency
® Maximum 82586 wait state: 300 nanoseconds
• Maximum Micro Channel wait state: 700 nanoseconds