MT92220 Datasheet, PDF (35/210 Pages) Zarlink Semiconductor Inc – 1023 Channel Voice Over IP/AAL2 Processor

Data Sheet
MT92220
Field
Description
CC
CRC Check Enable. This should always be set to ‘1’ if communicating with an AAL5
agent, and set to ‘0’ if this structure is receiving from an Ethernet or POS agent.
V
Valid bit. When ‘0’, any cell arriving on this VC number will be discarded as if it never
arrived. Caution: this bit can be cached by hardware, so when it is cleared, the
rxaal5_empty_cache bit in registers must be set (it will be cleared by hardware when the
cache is empty).
1st Header
"0000" = VC starting with the LLC Header;
"0001" = VC starting with a PPP Header;
"0010" = VC starting with an IP Header;
"0011" = VC starting with an MPLS Unicast Header;
"0100" = VC starting with an MPLS Multicast Header;
"0101" = VC starting with an MPOA Tag;
"0110" = VC starting with a LANE-Ethernet/802.3 Header;
"0111" = VC starting with a UDP payload (with or without RTP);
others = reserved.
SIP
MPLS IP indicator.
“11” = reserved;
“10” = RTP/UDP payload;
“01” = IP,
“00” = must be looked-up.
This value can be overridden later in the packet parsing process by a binary tree look-up
using the MPLS label. Usually set to “00”.
AIP
MPOA IP indicator.
“11” = RTP/UDP payload,
“10” = IP, “01” = MPLS unicast,
“00” = must be looked-up.
This value can be overridden later in the packet parsing process by a binary tree look-up
using the MPOA tag. Usually set to “00”.
ER
ELAN Resolved. When ‘1’, any ELAN-ID present is considered resolved, and will not
have to be looked-up to generate a Flow Table Bit Pointer. Usually set to ‘0’.
P
Priority of packet. ‘0’ = LP; ‘1’ = HP.
Max Packet Size
Maximum packet size in bytes (inclusive), including link layer protocol headers and up.
Minimal value 128, maximum value 65535. This number never includes the ATM header,
but includes the PPP header in Packet over SONET, and includes the Ethernet header
and a 2-byte LANE header in Ethernet. This number never includes the frame CRC.
CRC-32
Calculated by hardware during packet reception. Used to compare with CRC inside the
received packet.
EPD
‘0’ = all is well; ‘1’ = Early Packet Discard. In this case, the packet will be thrown out when
the last cell is received. This can be set because the packet length exceeded the Max
Packet Size. This bit is only used by hardware; set to ‘0’ initially by software.
Packet Cell
Count
Counter of the number of cells contained in the packet so far. Should be reset to 000h.
This counter excludes the Next Cell Handle, since this handle has been seized for a cell
that has not yet arrived.
Next Cell Handle Pointer to the block that has been pre-allocated for storing the next cell payload when it is
received.
Table 12 - Fields and Description
Zarlink Semiconductor Inc.
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