rtl8100l Realtek Semiconductor Corporation, rtl8100l Datasheet - Page 46

• Manufacturer Part Number: rtl8100l
• Description: Fast Ethernet Controller
• Manufacturer: Realtek Semiconductor Corporation

9.8 Tx Encapsulation
While operating in 100Base-TX mode, the RTL8100B(L) encapsulates the frames that it transmits according to the 4B/5B
code-groups table. The changes of the original packet data are listed as follows :
9.9 Collision
If the RTL8100B(L) is not in full-duplex mode, a collision event occurs when the receive input is not idle while the
RTL8100B(L) transmits. If the collision was detected during the preamble transmission, the jam pattern is transmitted after
completing the preamble (including the JK symbol pair).
9.10 Rx Decapsulation
The RTL8100B(L) continuously monitors the network when reception is enabled. When activity is recognized it starts to process
the incoming data.
After detecting receive activity on the line, the RTL8100B(L) starts to process the preamble bytes based on the mode of
operation.
While operating in 100Base-Tx mode, the RTL8100B(L) expects the frame to start with the symbol pair JK in the first bye of the
8-byte preamble.
The RTL8100B(L) checks the CRC bytes and checks if the packet data ends with the TR symbol pair, if not, the RTL8100B(L)
reports an CRC error RSR.
The RTL8100B(L) reports a RSR<CRC> error in any of the following cases :
9.11 Flow Control
The RTL8100B(L) supports IEEE802.3X flow control to improve performance in full-duplex mode. It detects PAUSE packets
to achieve flow control tasks.
9.11.1. Control Frame Transmission
When the RTL8100B(L) detects that its free receive buffer is less than 3K bytes, it sends a PAUSE packet with
pause_time(=FFFFh) to inform the source station to stop transmission for the specified period of time. After the driver has
processed the packets in the receive buffer and updated the boundary pointer, the RTL8100B(L) sends the other PAUSE packet
with pause_time(=0000h) to wake up the source station to restart transmission.
9.11.2. Control Frame Reception
The RTL8100B(L) enters a back off state for a specified period of time when it receives a valid PAUSE packet with
pause_time(=n). If the PAUSE packet is received while the RTL8100B(L) is transmitting, the RTL8100B(L) starts to back off
after current transmission completes. The RTL8100B(L) is free to transmit the next packets when it receives a valid PAUSE
packet with pause_time(=0000h) or the backoff timer(=n*512 bit time) elapses.
2001-11-9
1. The first byte of the preamble in the MAC frame is replaced with the JK symbol pair.
2. After the CRC, the TR symbol pair is inserted.
1. In the 100Base-Tx mode, one of the following occur.
a. An invalid symbol (4B/5B Table) is received in the middle of the frame.
b. The frame does not end with the TR symbol pair.
Note: The PAUSE operation cannot be used to inhibit transmission of MAC Control frames (e.g. PAUSE packet). The N-way
flow control capability can be disabled, please refer to Section 6. EEPROM (93C46) Contents for a detailed description.
RSR<ISE> bit also sets.
46
RTL8100B(L)
Rev.1.41