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
288
Section 9: Ethernet MACs
Document
1250_1125-UM100CB-R
The management protocol is shown in
. This shows the two sides of the read (the MAC request and
the PHY reply) and the full sequence sent by the MAC for a write. Bits are marked Z where the line is not being
driven. Bits marked A form the five bit address of the PHY that the MAC is directing the command to (typically
the PHY chip will have some input pins to set the address it responds to). The bits marked R form the five bit
register address. The bits marked x are the transfer of the 16 bits being read or written. The two addresses
and data are sent most significant bit first.
Some PHY devices can signal interrupts when the link status changes. These may be connected through one
of the GPIO pins.
RMON C
OUNTERS
Each MAC has 32 RMON statistics gathering registers. They are all 32 bits wide except the byte counts which
are 64 bits wide. Zeros will be read in the top 32 bits if a 64 bit access is made to the 32 bit registers, so
software can treat them as all being 64 bit except for computing overflow. The registers may be cleared by
software writing 0 to them. The counters must be written when the interface is initialized, until a write has been
performed their behavior will be UNPREDICTABLE. A write of any value other than zero will set the counter to
that value and it will increment from there. If any counter overflows it will wrap to zero and continue to count.
The cntr_ovrfl_err bit is set and the counter number is written to the counter_addr field in the
mac_status
register. The RMON counters are only updated in Ethernet Mode.
Table 166: MAC to PHY Management Protocol
Protocol
Idle
Start
Op
Code
Device
Addr
Register
Addr
Turn
Around
Data
Idle
Read (MAC)
Idle
01
10
AAAAA
RRRRR
ZZ
ZZZZ ZZZZ ZZZZ ZZZZ
Idle
Read (PHY)
Idle
ZZ
ZZ
ZZZZZ
ZZZZZ
Z0
XXXX XXXX XXXX XXXX
Idle
Write (MAC)
Idle
01
01
AAAAA
RRRRR
10
XXXX XXXX XXXX XXXX
Idle
Write (PHY)
Idle
ZZ
ZZ
ZZZZZ
ZZZZZ
ZZ
ZZZZ ZZZZ ZZZZ ZZZZ
Idle
Table 167: RMON Counters
Number
(
offset from
00_1006_0000
)
Counter
Description
0
_0 -
+4000
_1 -
+5000
_2 -
+6000
Tx Byte Counter
This Counter counts the total number of bytes successfully transmitted by the
MAC. All bytes in the frame from the first destination address byte to the last
CRC byte are included in the count. Successful transmission of a packet is
defined by transmission of a packet without any errors such as collision,
underrun or detection of invalid byte valid in control field of FIFO. This is a 64 bit
count.
1
_0 -
+4008
_1 -
+5008
_2 -
+6008
Tx Collision Counter
This Counter counts the total number of collisions experienced by the MAC
since the counter was last cleared. The count includes late collisions and will
increment by 16 on an excessive collision.
2
_0 -
+4010
_1 -
+5010
_2 -
+6010
Tx Late Col. Counter
This Counter counts the total number of late collisions experienced by the MAC
since the counter was last cleared.
3
_0 -
+4018
_1 -
+5018
_2 -
+6018
Tx Ex. Col. Counter
This Counter counts the total number of excessive collisions experienced by
the MAC since the counter was last cleared. An excessive collision is defined
as 16 consecutive collisions during the attempt to transmit a particular packet.
The MAC will abort the packet transmission when it suffers excessive collisions.