DP83932CVF25 National Semiconductor, DP83932CVF25 Datasheet - Page 41

• Manufacturer Part Number: DP83932CVF25
• Manufacturer: National Semiconductor

Specifications of DP83932CVF25

• Operating Supply Voltage (typ): 5V
• Operating Supply Voltage (min): 4.75V
• Operating Supply Voltage (max): 5.25V
• Mounting: Surface Mount
• Pin Count: 132
• Lead Free Status / RoHS Status: Not Compliant

4 0 SONIC Registers
4 3 10 CAM Registers
The CAM registers described in this section are part of the
User Register set They are used to program the Content
Addressable Memory (CAM) entries that provide address
filtering of packets These registers except for the CAM
Enable register are unaffected by a hardware or software
reset
CAM Entry Pointer Register (CEP) The CEP is a 4-bit
register used by SONIC to select one of the sixteen CAM
entries SONIC uses the least significant 4-bits of this regis-
ter The value of 0h points to the first CAM entry and the
value of Fh points to the last entry
CAM Address Port 2 1 0 Registers (CAP2 CAP1
CAP0) Each CAP is a 16-bit read-only register used to ac-
cess the CAM cells Each CAM cell is 16-bits wide and con-
tains one third of the 48-bit CAM entry which is used by the
SONIC for address filtering The CAP2 register is used to
access the upper bits (
(
entry Given the physical address 60 50 40 30 20 10 which
is made up of 6 octets or bytes where 10h is the least
significant byte and 60h is the most significant byte (60h
would be the first byte received from the network and 10h
would be the last) CAP0 would be loaded with 2010h CAP1
with 4030h and CAP2 with 6050h
To read a CAM entry the user first places the SONIC in
software reset (set the RST bit in the Command register)
programs the CEP register to select one of sixteen CAM
entries then reads CAP2 CAP1 and CAP0 to obtain the
complete 48-bit entry The user can not write to the CAM
entries directly Instead the user programs the CAM de-
scriptor area in system memory (see Section 4 1 1) then
issues the Load CAM command (setting LCAM bit in the
Command register) This causes the SONIC to read the de-
scriptors from memory and loads the corresponding CAM
entry through CAP2-0
CAM Enable Register (CE) The CE is a 16-bit read write
register used to mask out or enable individual CAM entries
Each register bit position corresponds to a CAM entry
When a register bit is set to a ‘‘1’’ the corresponding CAM
entry is enabled When ‘‘0’’ the entry is disabled This regis-
ter is unaffected by a software reset and cleared to zero
(disabling all entries) during a hardware reset Under normal
operations the user does not access this register Instead
the user sets up this register through the last entry in the
CAM descriptor area The SONIC loads the CE register dur-
ing execution of the LCAM Command
CAM Descriptor Pointer Register (CDP) The CDP is a
15-bit read write register The LSB is unused and always
reads back as 0 The CDP is programmed with the lower
MSB
47
k
47
31 16
CAP2
l
) and CAP0 the lower bits (
32 31
Destination Address
k
47 32
CAP1
l
) CAP1 the middle bits
(Continued)
16 15
k
15 0
l
) of the CAM
CAP0
LSB
0
0
41
address (A
block in the CAM descriptor area (CDA) of system memory
SONIC uses the contents of the CDP register when access-
ing the CAM descriptors This register must be programmed
by the user before issuing the LCAM command During exe-
cution of the LCAM Command SONIC concatenates the
contents of this register with the contents of the URRA reg-
ister to form the complete 32-bit address During the Load
CAM operation this register is incremented to address the
fields in the CDA After the Load Command completes this
register points to the next location after the CAM Descriptor
Area
CAM Descriptor Count Register (CDC) The CDC is a
5-bit read write register It is programmed with the number
of CAM descriptor blocks in the CAM descriptor area This
register must be programmed by the user before issuing the
LCAM command SONIC uses the value in this register to
determine how many entries to place in the CAM during
execution of the LCAM command During LCAM execution
SONIC decrements this register each time it reads a de-
scriptor block When the CDC decrements to zero SONIC
terminates the LCAM execution Since the CDC register is
programmed with the number of CAM descriptor blocks in
the CAM Descriptor Area the value programmed into the
CDC register ranges 1 to 16 (1h to 10h)
4 3 11 Tally Counters
The SONIC provides three 16-bit counters used for monitor-
ing network statistics on the number of CRC errors Frame
Alignment errors and missed packets These registers roll-
over after the count of FFFFh is reached and produce an
interrupt if enabled in the Interrupt Mask Register (IMR)
These counters are unaffected by the RXEN bit in the CR
but are halted when the RST bit in the CR is set The data
written to these registers is inverted before being latched
This means that if a value of FFFFh is written to these regis-
ters by the system they will contain and read back the value
0000h Data is not inverted during a read operation The
Tally registers therefore are cleared by writing all ‘‘1’s’’ to
them A software or hardware reset does not clear the tally
counters
CRC Tally Counter Register (CRCT) The CRCT is a 16-bit
read write register This register is used to keep track of the
number of packets received with CRC errors After a packet
is accepted by the address recognition logic this register is
incremented if a CRC error is detected If the packet also
contains a Frame Alignment error this counter is not incre-
mented
FAE Tally Counter Register (FAET) The FAET is a 16-bit
read write register This register is used to keep track of the
number of packets received with frame alignment errors
After a packet is accepted by the address recognition logic
this register is incremented if a FAE error is detected
Missed Packet Tally Counter Register (MPT) The MPT is
a 16-bit read write register After a packet is received this
counter is incremented if there is (1) lack of memory re-
sources to buffer the packet (2) a FIFO overrun or (3) a
valid packet has been received but the receiver is disabled
(RXDIS is set in the command register)
k
15 1
l
) of the first field of the CAM descriptor