PCAP01 datasheet(91/96 Pages) SCIOSENSE

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PCapØ1Ax-0301

7-2

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7.1

Bug Report

7.1.1

I2C Bug

Description

In case PCap01A is not the only device on the I2C bus, we have the following errors:

Table 7-1: Communication between Master and some Slave other than PCap01

Situation

Expected behavior

Actual behavior

Conclusio

Master initializes

communication with

another slave than

PCap01

PCap01 should remain

silent like it were

absent from the bus.

PCap01 acknowledges any

address byte. It sets the ACK

bit like if it had been called

with its own address (1)(2)

wrong

Master has estab-lished

commu-ni-ca-tion with

another slave and is

writing data to, or reading

data from it.

PCap01 should remain

neatly off the SDA line.

PCap01 acknowledges any

data byte in parallel to

slave's(2) and master's(3)

ACK or despite their

respective NACK

wrong

PCap01 should ignore

the data bits

themselves

PCap01 does not listen to

those data bits that are sent

to others.

right

(1) If the requested slave is present and ready to respond, this will be tolerable.

(2) NACK (refused acknowledge) no longer exists in this kind of a situation.

(3) This kind of “meddling with the master‘s business“ may trouble the master (caution with

integrated i2C controllers). Master is requested not to leave its master status, but to remain

master and to issue a STOP condition.

Preliminary suggestions



Take the SPI interface, if possible. No problem detected on SPI.



If you need the I2C interface, restructure your network so that PCap01 is

connected single-slave to the master.



If you need I2C and cannot avoid a multi-slave bus structure, be aware of the

restrictions to the bus protocol, described in this report

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