LAN TRANSCEIVER

M54617P

MITSUBISHI <CONTROL / DRIVER IC>

FUNCTION

Pin function

Pin No.

Pin name

I/O

Function

Input

Data signal input pin

STB

Input

Standby signal input pin

L: standby mode, H: normal operation

ERR

I/O

Error signal output pin and error reset input pin

“L” level output when abnormal transmission route is detected

Error reset with “H” level input when in the standby mode

Output

Signal output pin from transmission route

Input

Grounding pin

BUS(-)

I/O

Signal output pin to transmission route and signal input pin from transmission route (negative logic)

BUS(+)

I/O

Signal output pin to transmission route and signal input pin from transmission route (positive logic)

Power supply pin

Input

1

2

3

4

5

6

7

8

ABNORMALITY DETECTION OF TRANSMISSION

ROUTE AND COMMUNICATION FUNCTION

The M54617P uses its driver overcurrent detection function and

transmission signal logic abnormality function to perform the

abnormality detection of the transmission route, and outputs error

signal (ERR(3 pin) = “L”).

In addition, switching the signal that is output to Rx pin (pin 4)

according to

the

abnormality occurrence status permits

communication after abnormality has occurred.

(1) Overcurrent detection

BUS(+) pin (pin 7) and BUS(-) pin (pin 6) drivers of M54617P are

equipped with an overcurrent detection circuit. When overcurrent

flows to a driver, the driver is turned OFF to output error signal

(ERR (pin 3) = “L”). Once an overcurrent is detected, the driver

maintains the OFF status until the error is reset.

In addition, each driver of BUS(+) pin (pin 7) and BUS(-) pin (pin 6)

is independent, and both may be turned OFF depending upon the

abnormality occurrence status.

A built-in filter for the prevention of malfunction due to overcurrent

when the driver is turned ON does not permit the detection of the

overcurrent status for a short time (several hundred ns). Detection

current is set to about 180mA.

(2) Logic abnormality detection

The M54617P transmission signals operate in the opposite phase

to each other, and abnormal transmission route is detected by

comparing these signals. Upon comparing respective signals after

a set time on the basis of the edge of transmission routes BUS(+)

and BUS(-), any disagreement is

regarded as

abnormal

transmission, and error signal (ERR (pin 3) = “L”) is output. In order

to be well timed with that edge as a new standard, abnormality is

detected when signal disagreement continues for more than a set

time. Setting time is set to about 4.2

µs.

Logic abnormality detection does not cope with more than one

error mode.

Detection of logic abnormality alone does not allow the driver to be

turned OFF. Abnormality detection allows the driver to be turned

OFF only when overcurrent is detected.

(3) Communication function

The M54617P ordinarily outputs the differential signals of BUS(+)

(pin 7) and BUS(-) (pin 6). When abnormality is detected, signals to

be output to Rx pin (pin 4) are switched according to the status.

When overcurrent is detected, the driver or the transmission route

in which overcurrent is detected is considered abnormal, and error

signal is

output, and concurrently the signal of

another

transmission route is output to Rx output (pin 4).

As described in the above section (1), both drivers are turned OFF

in some cases. In these cases, Rx output (pin 4) is fixed to “L”.

When logic abnormality is detected, error signal (ERR (pin 3) = “L”)

is output, and concurrently Rx output (pin 4) is turned to “L”. After

error signal is output, the transmission route in which the edge of

transmission signals is detected is considered normal, and such

signal is output to Rx output (pin 4).

In switching operation of error signal output and Rx output the

priority is given to overcurrent detection over logic abnormality

detection.