User Manual
BCM1250/BCM1125/BCM1125H
10/21/02
B r o a d c o m C o r p o r a t i o n
Document
1250_1125-UM100CB-R
Section 9: Ethernet MACs Page
303
32
bypass_sel
1'b0
When this bit is set the MAC is bypassed and Packet FIFO mode is enabled. This
provides a simple FIFO interface, backed by the DMA engine. See
Bit Packet FIFO Operation” on page 294
for details.
33
hdx_en
1'b0
When this bit is set the MAC will operate in half-duplex mode, when the bit is clear
it will run full-duplex. The MAC supports both full and half-duplex operation at all
speeds.
Used in Ethernet mode only.
35:34
speed_sel
2'b0
This field sets the speed the MAC will operate.
00: 10 Mbps
- the TCLK input should be 2.5 MHz.
01: 100 Mbps - the TCLK input should be 25 MHz.
10: 1000 Mbps - the transmit clock will be supplied by the interface. The
reference clock input should be 125 MHz.
11: Reserved
Used in Ethernet mode only. Must be set to 10 for Packet FIFO modes.
36
tx_clk_edge
1'b0
This selects the edge of the transmit clock that is used to send the data. Normally
the rising clock edge should be used. The falling edge can be used to support old
10 Mbps PHY chips that require the full hold time specified in the original IEEE
specification.
0: The rising edge of the clock is the active one.
1: The falling edge of the clock is the active one.
Used in Ethernet and Packet FIFO modes.
37
loopback_sel
1'b0
When this bit is set an internal loopback path is enabled, connecting the
transmitter and receiver GMII pins.
Used in Ethernet and 8 bit Packet FIFO modes.
38
fast_sync
1'b0
This bit must be set for normal operation. (It defaults to 0 so software should be
sure to set it before starting the MAC.)
Used in Ethernet and Packet FIFO modes.
39
ss_en
1'b0
This bit must always be set. (Broadcom Use Only debug bit). (It defaults to 0 so
software should be sure to set it before starting the MAC.)
Used in Ethernet and Packet FIFO modes.
41:40
bypass_cfg
2'b0
This field sets the strobe signals that are used on both transmit and receive
interfaces in Packet FIFO mode.
00: GMII style
01: Encoded
10: SOP flagged (not valid in 16 bit Packet FIFO mode)
11: EOP flagged (not valid in 16 bit Packet FIFO mode)
Used in Packet FIFO modes.
42
bypass_16
1'b0
Set for 16 bit Packet FIFO mode, clear for 8 bit Packet FIFO mode.
The interface behavior will become UNDEFINED if this bit is set for MAC 1.
Setting this bit for MAC 0 will cause the pins to change from their eight bit E0 and
E1 configuration to the 16 bit F0 configuration.
Setting this bit for MAC 2 will cause the pins to change from their eight bit E0, E1
and E2 configuration to the 16 bit F1 configuration.
This bit must be set to reflect the external connection.
Used in Packet FIFO modes.
Table 176: MAC Configuration Registers
(Cont.)
mac_cfg_0 -
00_1006_4100
mac_cfg_1 -
00_1006_5100
mac_cfg_2 -
00_1006_6100
This register is used in both Ethernet and Packet FIFO modes
Bits
Name
Default
Description