
Switched Fast Ethernet Controller
Revision 1.2
13
MAC0LED[5:0]
O
MAC LEDs for Port 0: Active LOW Parallel LED outputs for port 0
bit [0]: Port Status (operation according to LEDMode)
bit [1]: Transmit In Progress (TxEn active)
bit [2]: Receive In Progress (RxDV active)
bit [3]: Collision (Col active)
bit [4]: Full Duplex (port configured to Full Duplex)
bit [5]: Receive Buffer Full (programmable limit exceeded)
An external driver is required to drive the LEDs.
MAC1LED[5:0]
O
MAC LEDs for Port 1: Active LOW Parallel LED outputs for port 1
Same as MAC0LED
RstQueue*
I
Reset Transmit Queues: When asserted, all internal transmit and receive
queues are cleared. All GT-48002A state machines are moved to their initial
state.
EnDev*
I
Enable Device: Enables serial and PCI ports. When asserted LOW, all serial
ports and the PCI port are active. When deasserted, the ports and the PCI are
disabled (see Section 3.1).
Scan*
I
Scan: This pin together with TriState* indicate the GT-48002A mode of opera-
tion as follows:
Factory test modes are reserved and are not to be used in-system. Failure to
observe this restriction could result in damage to the device.
TriState*
I
Tri-State: This pin together with Scan* indicate the GT-48002A mode of oper-
ation as described above.
DisWD*
I
Disable Watchdog Timer: Active LOW. DisWD* controls the enabling
(HIGH) or disabling (LOW) of the Tx Watchdog Timer on all ports.
DisBufThr*
I
Buffer Threshold: Active LOW. This pin externally enables or disables the
buffer threshold. When HIGH, the buffers allocated to the ports and the PCI
are limited to the number written in the Rx Buffer Threshold Register. When
LOW, the buffers are dynamically allocated to the ports and the PCI bus (i.e.
there is no limitation on the buffers’ allocation.)
Limit4
I
Backoff Algorithm: This pin selects the number of retransmit attempts after a
collision will occur before the back-off alogorithm is restarted. When LOW, 16
retransmit attempts after a collision must occur before the back-off alogorithm
is restarted (802.3 standard). When HIGH, 4 retransmit attempts after a colli-
sion must occur before the back-off alogorithm is restarted (more aggressive.)
Sy m b ol
Ty p e
De s c ri pti o n
Sc an*
Tr i S t a t e *
Mode
1
Normal operation
0
1
Factory test mode (reserved)
1
0
The GT-48002A drives all out-
puts and I/O pins to high imped-
ance.
0
Factory test mode (reserved)