Motorola MVME712A/D3 User Manual download pdf (Page 191)

LAN Coprocessor for Ethernet (LANC) Tests

MVME167BUG/D3 3-147

Internal Loopback - ILB

The 82596 has three modes of loopback: Internal Loopback, External Loopback

with the LPBK pin activated, and External Loopback with the LPBK pin not

activated. The LPBK pin is connected to the accompanying Ethernet Serial

Interface (ESI - 82C501AD) chip. The ESI is then connected to the pulse

transformer (PE64102), which in turn is connected to the Ethernet Connector.

In Internal Loopback mode the 82596 disconnects itself from the serial link and

logically connects TXD to RXD and TXC to RXC. The TXC frequency is

internally divided by four during internal loopback operation.

In External Loopback mode the 82596 transmits and receives simultaneously

at a full rate. This allows checking external hardware as well as the serial link

to the transceiver interface. The LPBK pin is used to inform the external

hardware (ESI) of the establishment of a transmit to receive connection.

This test verifies that the 82596 can be operated in the ÒInternal LoopbackÓ

mode. Basically, the test sets up a data packet (incrementing data pattern) to

be transmitted, transmits it, and waits for the reception of the data. Once the

data is received, the data is verified to the data transmitted. This transmit to

receive loop is performed 32 times. This loop count can be changed via the CF

command (CF LANC).

Command Input:

167-Diag>LANC ILB

Response/Messages:

After the command has been issued, the following line is printed:

LANC ILB: Internal Loopback.................. Running --->

If all parts of the test are completed correctly, then the test passes:

LANC ILB: Internal Loopback.................. Running ---> PASSED

If any failures occur, the following is displayed (more descriptive text then

follows):

LANC ILB: Internal Loopback.................. Running ---> FAILED

(error message)

Once the data packet has been set up to be transmitted, the test instructs the

82596 (through the Command Unit) to transmit the data packet. This failure is

the result of the 82596 completing with a transmit data error.

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Motorola MVME712A/D3 User Manual Page 191