LAN83C183 Datasheet, PDF (43/113 Pages) SMSC Corporation – FAST ETHERNET PHYSICAL LAYER DEVICE

1.8 JABBER
A jabber condition occurs in 10 Mbits/s mode when the transmit packet exceeds a
predetermined length. When jabber is detected, the TP transmit outputs are forced
to the idle state, a collision is asserted, the JAB register bit is set in the MI serial port
Status register, and the JAB bit is set in the MI serial port Status Output register.
To disable the jabber function, set the Jabber Disable bit (JAB_DIS) in the MI serial
port Configuration 2 register
The jabber function is disabled in the 100 Mbits/s mode.
1.9 AUTOMATIC JAM
This section describes automatic JAM operation for both 100 and 10 Mbits/s
operation.
1.9.1 100 Mbits/s JAM
The LAN83C183 has an automatic JAM feature that causes the device to
automatically transmit a JAM packet if receive activity is detected. If automatic JAM
is enabled, the following JAM packet is transmitted on TPO± when the RX_EN/JAMn
pin is asserted LOW and receive activity is detected on the TP inputs (expressed in
5B code words):
/J/K/5/5/5/5/5/5/5/5/5/5/5/5/5/D/H/H/H/H/H/H/H/H/T/R/
This automatic JAM feature is enabled when the RX_EN/JAM pin is programmed to
be a JAM input. To configure the RX_EN/JAMn pin as a JAMn input, set the
R/J_CFG bit in the MI serial port Configuration 2 register.
1.9.2 10 Mbits/s JAM
The JAM feature for the 10 Mbits/s mode is identical to that of the 100 Mbits/s mode
except that the JAM packet transmitted on TPO± consists of the standard 62-bit
preamble (alternating 1s and 0s) followed with the SFD pattern (0b11), which is then
followed with 32 bits of alternating 1s and 0s.
SMSC DS – LAN83C183
43
Rev. 12/14/2000