MK50H28 datasheet(46/64 Pages) STMICROELECTRONICS

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4.4.2.1 User Mode (Auto LMI Mode) - Continued

In User Mode the MK50H28 will perform the following functions:

1. Transmit STATUS ENQUIRY frames at an interval determined by the nT1 timer.

2. After every nN1 transmissions of STATUS ENQUIRY with Report Type of ”LIV Only” the

MK50H28 transmits a STATUS ENQUIRY with Report Type of ”Full Status”.

3. When a STATUS frame is received in response to a STATUS ENQUIRY, the receive sequence

number received from the Network side is checked against the User send sequence number.

4. A received Full STATUS frame will be stored into the LMI channel buffer, the sequence number

checking will be performed, and its reception will be indicated via Provider Primitive 13.

5. A received Asynchronous STATUS frame will be stored into the LMI channel buffer and its recep-

tion will be indicated via Provider Primitive 14.

6. An available transmit or receive buffer is not required for the MK50H28 automatic processing of

”LIV only” frames.

7. A STATUS ENQUIRY frame (Full or LIV only) received in User mode will be discarded and the

Discarded Frames Counter in Context Table entry 0 will be incremented.

4.4.2.2 Network Mode (Auto LMI Mode)

The following procedure should be followed for establishing a link.

1. Make sure that the ACTIVE bit in the ALT is set for the LMI channel.

2. Issue the Auto LMI Primitive 7 with UPARM = 1 through CSR1 (write 5700H) to place the device

in Auto LMI Network Mode.

In Network Mode the MK50H28 will perform the following functions:

1. Automatically responds to STATUS ENQUIRY with Report Type of ”LIV Only” by transmitting a

STATUS frame with Report Type of ”LIV Only” along with restarting the nT2 timer.

2. 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 ready to transmit the Full STATUS frame).

3. An available transmit or receive buffer is not required for the MK50H28 automatic processing of

”LIV only” frames.

4. Asynchronous STATUS frames may be transmitted by placing the data to be transmitted into the

appropriate buffer and issueing Primtive 11 with UPARM=2.

5. A STATUS frame (Full, LIV Only, or Asynchronous) received in Network mode will be discarded

and the Discarded Frames Counter in Context Table entry 0 will be incremented.

4.4.2.3 Bi-directional Procedures (Auto LMI Mode)

The following procedure should be followed to implement the Optional Bi-directional Procedures

1. Make sure that the ACTIVE bit in the ALT and TXRDY in the CT are set for the LMI channel.

2. Make sure that the Transmit Ring Pointer, Current Transmit Descriptor and address field informa-

tion in the CT is valid. This is necessary for transmission of Full STATUS frame.

3. Issue the Auto LMI Primitive with UPARM = 2 through CSR1 (write 6700H) to place the device in

Bi-directional Mode. In Bi-directional Mode the MK50H28 will transmit STATUS ENQUIRY

frames with one set of sequence numbers and use a separate set of sequence numbers to proc-

ess received STATUS ENQUIRY frames. STATUS frames will be sent with the separate set of

sequence numbers differing from those used in the processing of recived STATUS frames.

In Bi-directional Mode the MK50H28 will perform the following functions:

1. The MK50H28 supports this operation using separate User and Network sequence numbers and

N392 and N393 counters.

2. The MK50H28 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.

MK50H28

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