Agilent Technologies HDMP-3001 User Manual

Page 22

EOS_D_SUM

group indicates

that at least one of the delta sig-
nals below is unmasked and set.
NEW_RX_MIN_ERR,
NEW_RX_MAX_ERR,
NEW_RX_OOS_ERR,
NEW_RX_FORM_DEST_ERR,
NEW_RX_FIFO_UR_ERR,
NEW_RX_FIFO_OF_ERR,
NEW_RX_FCS_HEC_ERR,
NEW_TX_FIFO_UR_ERR,
NEW_TX_FIFO_OF_ERR,
NEW_TX_ER_ERR,
NEW_TX_MII_ALIGN_ERR

3.7.4 APS_INTB
RX_APS_INT interrupt message
for APS (K1 and K2) indicates that
at least one of the RX_K1_D,
RX_K2_D, K1_UNSTAB_D is one
and the corresponding mask bits
and RX_APS_INT_MASK are zero.

3.8 Data Processing
The LAPS and GFP TX Processing
refers to the encapsulation of the
MAC (Media Access Control)
frames coming from the MII (Me-
dia Independent Interface, see
IEEE 802.3 specification) into the
LAPS/GFP frames, which are then
sent to the Line Side Interface
(SONET/SDH). Figure 9 shows an
Ethernet MAC frame, and Figure
10 a LAPS frame with a MAC pay-
load.

3.8.1 LAPS Processing
The Transmit LAPS Processor
provides the insertion of packet-
based information into the STS
SPE. It provides packet encapsu-
lation, FCS field generation,
inter-packet fill and scrambling.
The Transmit LAPS Processor
performs the following functions:

•

Encapsulates packets within
an LAPS frame. Each packet is
encapsulated with a start flag
(0x7E), a 32-bit FCS field,
Address, Control and SAPI

PREAMBLE

START OF FRAME DELIMITER

DESTINATION ADDRESS (DA)

SOURCE ADDRESS (SA)

LENGTH/TYPE

MAC CLIENT DATA

FCS

7 OCTETS

1 OCTET

6 OCTETS

2 OCTETS

46 - 1500 OCTETS

4 OCTETS

BIT 7

BIT 0

MSB

LSB

OCTETS WITHIN

FRAME ARE

TRANSMITTED FROM

TOP TO BOTTOM

FLAG (0x7E)

ADDRESS (0x04)

CONTROL (0x03)

SAPI MSB (0xFE)

SAPI LSB (0x01)

DESTINATION ADDRESS (DA)

SOURCE ADDRESS (SA)

LENGTH/TYPE

MAC CLIENT DATA

FCS OF MAC

FCS OF LAPS

FLAG (0x7E)

1 OCTET

BIT 8

BIT 1

MSB

LSB

MSB

MAC
FRAME

OCTETS WITHIN

FRAME ARE

TRANSMITTED FROM

TOP TO BOTTOM

6 OCTETS

2 OCTETS

46 - 1500 OCTETS

4 OCTETS

Figure 9. An Ethernet MAC frame

Figure 10. The format of a LAPS frame with a MAC payload

fields, and an end of field flag
(0x7E). All fields except the
start flag can be disabled
through configuration.

•

Optional self-synchronous
transmit payload scrambler
(X

+1 polynomial).

•

Transparency processing
(octet stuffing for Flags &
Control Escape). Byte stuffing
occurs between start and end
of field flags. Stuffing replaces

each byte within a frame that
matches the flag or control
code bytes with a two-byte
sequence.

•

Provides the ability to insert
FCS errors for testing under
SW control.

•

Provides for selectable
treatment of FIFO underflow.
A FIFO underflow condition
occurs when a TX FIFO empty
occurs prior to the end of a