BCM1250/BCM1125/BCM1125H
User Manual
10/21/02
B r o a d c o m C o r p o r a t i o n
Page
294
Section 9: Ethernet MACs
Document
1250_1125-UM100CB-R
There are four formats that are available for the 8 bit Packet FIFO to signal data validity and packet boundaries.
In all cases data and control signals are sampled on the rising edge of the clock. On the transmit side the GMII
TXEN (enable) and TXER (error) signals are used as two control signals that are used to send out the framing
information, and on receive the RXDV (data valid) and RXER (error) pins are used to receive the framing
information.
8-B
IT
GMII S
TYLE
P
ACKET
FIFO
The GMII style of Packet FIFO mode is shown in
. The packet data is framed by the
TXEN or RXDV signal. The first byte that has it active is marked as the start of a packet and the last byte that
has it active is the end of the packet, all bytes between are valid and part of the packet. The TXER or RXER
signal can be used to signal an error whenever the frame signal is active.
Figure 60: 8-bit Packet FIFO GMII Style
The error pin TXER/RXER may be used to signal that a packet has an error. It should be asserted when the
error is detected and remain high until the enable signal falls.
TXEN/RXDV
TXER/RXER
TXD/RXD[7:0]
TCLKO/RCLK
55
Table 170: Codes for GMII Packet FIFO Mode
TXEN / RXDV
TXER / RXER
Valid Data, Start of Packet
0->1 at start of cycle
0
Valid Data
1
0
Valid Data, End of Packet
1->0 at end of cycle
0
Error
1
1 held until TXEN/RXDV falls