MK50H28 datasheet(13/64 Pages) STMICROELECTRONICS

13 / 64 page

3.2.8 Modes of Protocol Operation

The User mode of operation is entered by issuing

an Auto LMI primitive 7 with UPARM=0. In this

mode, the device transmits STATUS ENQUIRY

messages to the network with an interval deter-

mined by the nT1 timer. After every nN1 transmis-

sions of STATUS ENQUIRY with Report Type of

”Length Integrity Verification (LIV) Only” the

MK50H28 transmits a STATUS ENQUIRY with

Report Type of ”Full Status”.

When a STATUS frame is received in response to

a STATUS ENQUIRY(LIV only), the receive se-

quence number received from the Network side

is checked against the User send sequence num-

ber. A received Full STATUS frame will be stored

into the LMI/LIV channel buffer, the sequence

number checking will be performed, and its recep-

tion will be indicated to the host via Provider

Primitive 13. An available transmit or receive buff-

er is not required for the MK50H28 automatic

processing of ”LIV only” frames.

A received Asynchronous STATUS frame will be

stored into the LMI/LIV channel buffer and its re-

ception will be indicated to the host via Provider

Primitive 14. If a STATUS ENQUIRY frame (Full

or LIV only) is received in this mode of operation,

the MK50H28 will discard the frame and incre-

ment the Discarded Frames Counter in Context

Table enrtry 0. Also see nT1 description in 4.2.2

Timer/Counter section.

The Network mode of operation is entered by is-

suing an Auto LMI primitive 7 with UPARM=1. In

this mode, the device automatically responds to

STATUS ENQUIRY with Report Type of ”Length

Integrity Verification (LIV) Only” by transmitting a

STATUS frame with Report Type of ”LIV Only”

along with restarting the nT2 timer. An available

transmit or receive buffer is not required for the

MK50H28 automatic processing of ”LIV only”

frames.

When a STATUS ENQUIRY with Report Type of

”Full Status” is received, the device issues the

LMI Received primitive 13 (with PPARM=1) and

expects the host to respond with an LMI Status

Request Primitive 11 with UPARM=0 (when the

host is ready to transmit the Full STATUS frame).

Asynchronous STATUS frames may be transmit-

ted by placing the data to be transmitted into the

appropriate buffer and issueing Primtive 11 with

UPARM=2. If a STATUS frame (Full, LIV Only, or

Asynchronous) is received in this mode of opera-

tion, the MK50H28 will discard the frame and in-

crement the Discarded Frames Counter in Con-

text Table enrtry 0. Also see nT2 description in

4.2.2 Timer/Counter section.

The Bi-directional Network Procedures mode

is entered by issuing an Auto LMI primitive 7 with

UPARM=2. The MK50H28 supports this opera-

tion using separate User and Network sequence

numbers and N392 and N393 counters. In this

mode, the device transmits STATUS ENQUIRY

messages with a User set of sequence numbers

at an interval determined by the nT1/T391 timer.

The expected response is a STATUS frame with

corresponding sequence numbers. After every

nN1/N391 transmissions of STATUS ENQUIRY

with Report Type of ”LIV Only”, the MK50H28

transmits a STATUS ENQUIRY with Report Type

of ”Full Status”.

A received Full STATUS frame will be stored into

the LMI/LIV channel buffer, the sequence number

checking will be performed, and its reception will

be indicated to the host via Provider Primitive 13.

A received Asynchronous STATUS frame will be

stored into the LMI/LIV channel buffer and its re-

ception will be indicated to the host via Provider

Primitive 14.

In this mode, the device also automatically re-

sponds to STATUS ENQUIRY (”LIV Only”) by

transmitting a STATUS (”LIV Only”) frame along

with restarting the nT2 timer. When a ”Full Status”

Table 1 - MK50H28 Frame Types

INFORMATION ELEMENT

NAME

DIRECTION

Message Type Encoding

MSB

LSB

Message Type

STATUS_ENQUIRY

User -> Network

STATUS

Network -> User

UPDATE_STATUS

Network <-> User

NOTES:

1. STATUS_ENQUIRY Frame - This Frame has the format as shown in Figure 4.

2. STATUS Frame - This Frame has the format as shown in Figure 5. If Full STATUS information is to be sent, the

host must specify the PVC_STATUS Information Element(s) in the transmit buffer(s).

3. Asynchronous STATUS Frame - This Frame has the format as shown in Figure 6. The host must specify the PVC_

STATUS Information Element in the transmit buffer(s).

4. UPDATE_STATUS Frame - Not used in most current applications, MK50H28 supported for backwards compatibility.

MK50H28

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