MK50H25PLCC datasheet(41/64 Pages) STMICROELECTRONICS

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4.4.2 Active Link Setup

The following procedure should be followed to actively establish a link.

1. Issue Connect Request primitive (UPRIM=6) through CSR1. The MK50H25 will attempt to establish a

logical link. It does this by sending a SABM/P=1 frame, and repeats sending it at T1 timer intervals un-

til a response is received or N2 have been sent (in which case it would issue PPRIM=14 with

PPARM=1).

2. Wait for a Connect Confirmation primitive (PPRIM=7) from the MK50H25 (indicating reception of UA

frame in response to SABM sent).

3. If a Connect Confirmation primitive is received, a link has been established.

4. If a Disconnect Indication primitive (PPRIM=14) is received, the MK5025 has been unable to establish

a link. The reason will be in the PPARM field of CSR1.

4.4.3 Passive Link Setup

The following procedure should be followed for passively establishing a link.

1. Issue a Disconnect Request primitive (UPRIM=14). If issued with UPARM=0, a DM/F=0 frame will be

sent; if issued with UPARM=1, a DISC/P=0 frame will be sent to the remote station requesting link

setup. This step is optional in many cases, but some networks require either a DM or DISC be sent to

initiate passive link setup.

2. Wait for a Connect Indication primitive (PPRIM=6) from the MK50H25.

3. If a Connect Indication primitive is received (indicating SABM frame has been received), issue a Con-

nect Response primitive to indicate willingness to establish the link (causes MK50H25 to respond with

a UA frame). The link is now established.

4. If no Connect Indication primitive is received, the remote station is not trying to establish a link.

4.4.4 Refusing Link Setup

The following procedure should be followed when refusing link establishment.

1. A Connect Indication primitive received indicates a request by the remote station to establish a link.

2. Issue a Disconnect Request primitive to refuse to establish the link (causes MK50H25 to respond with

a DM or DISC frame depending on value of UPARM).

4.4.5 Sending Data

Use the following procedure to send a frame:

1. Wait for the OWNA bit of the current transmit descriptor to be cleared, if it is not already.

2. Fill the buffer associated with the current transmit descriptor with the data to be sent, or set the de-

scriptor buffer address to any already filled buffer.

3. Repeat steps 1 & 2 for next buffer if chaining is necessary, setting SLF, ELF and MCNT appropriately.

4. Set the OWNA bit for each descriptor used.

5. Go on to next descriptor. The OWNA bits will be cleared when data has been sent successfully and

acknowledged. In Transparent Mode, OWNA bits are cleared immediately after frame transmission.

4.4.6 Receiving Data

The following procedure should be followed when receiving a frame:

1. Make sure the OWNA bit of the current receive descriptor is clear.

2. Read data out of the buffer associated with the current receive descriptor.

3. Set the OWNA bit of the current receive descriptor.

4. If the ELF bit of the current receive descriptor is clear, then go on to the next descriptor and repeat

the above steps appending data from each buffer until a descriptor with the ELF bit set is reached.

4.4.7 Link Disconnect

The following procedure should be followed to disconnect an established link.

1. Issue the Disconnect Request primitive to the MK50H25.

2. A Disconnect Confirmation primitive (PPRIM=15) will be issued after successful disconnection, and the

MK50H25 will go into Normal Disconnected state.

MK50H25

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