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5.10.1 IIC Special mode function

The IIC function is enabled and disabled by

sending a report with the following structure with

ReportID=1 to interface 1:

enable=$01 enables the IIC function, $00 disables

it. Other values are reserved for future use.

Upon enabling IIC the SDA and SCL pins are

pulled high and are no longer under control of

interface 0. Disabling IIC does return the pins

under control of interface 0 and pulls them high

initially.

flags contains some configuration information:

7 - Disable Pull Ups (1 = disable)

6 - unused, write zero

5 - unused, write zero

4 - unused, write zero

3 - unused, write zero

2 - unused, write zero

1 - speed bit 1

0 - speed bit 0

Bit 7 "Disable Pull Up" allows operation with

external pull up resistors and lower voltage levels.

When this bit is set the internal pull up resistors of

the IIC pins are disabled and the SDA/SCL pins

work as open drain. The pull up resistors can not

be enabled again while the IIC function is active.

Disabling and again enabling the IIC function is

necessary to change the status of the pull-up

resistors back to active.

Bits 0 and 1, speed of the IIC clock.

0 = standard (93.75kHz)

1 = fast (375kHz)

2 = slow (46.8kHz)

A write request to the IIC is send with ReportID=2

and has the following format:

flags contains the following bits:

7 - Generate Start

6 - Generate Stop

5 - data count MSB

4 - data count

3 - data count

2 - data count

1 - data count

0 - data count LSB

If bit 7 - "Generate Start" is set a start signal (SDA

falling edge while SCL is high) is generated on the

IIC prior to sending out the first data byte.

Bit 6 - "Generate Stop" causes a stop signal (SDA

goes high while SCL is high) to be generated after

sending the last valid data byte of this report.

"data count" gives the number of valid data bytes

in the report. The number may range from 1 to 62,

higher values cause the report to be ignored.

To do write transactions that are longer than 62

bytes, send the first report with just the "Generate

Start" bit set, then send additional reports with

neither bit 6 or 7 set until the last report is send

which has the "Generate Stop" bit set.

Clock stretching by the slave to slow down data

transfer is supported by IO-Warrior56.

Sending just the address byte in write mode and

then terminating the transfer with a stop condition

is not supported by IOW56. Trying to send such a

command results in an error being returned. Errors

are returned also when another start condition is

attempted before issuing a stop, or if data is send

without having a valid start condition.

Any write transactions are acknowledged by a

report via interrupt-in endpoint 3:

flags contains the following bits:

7 - Error bit, 1 = error

6 - Arb loss bit, 1 = Arbitration lost

5 - data count MSB

4 - data count

3 - data count

2 - data count

1 - data count

0 - data count LSB

"data count" indicates the last byte that was

successfully transfered and acknowledged by the

slave (if any).

An error is indicated when the slave does not

acknowledge a transfer, or an invalid start/stop

condition was requested.

If another master starts transmission on the bus at

the same time and IO-Warrior56 loses the bus due

to a collision, an Arb Loss is returned.

To resolve an Arb Loss the transfer has to be

initiated again.

ReportID

$01 out

enable flags

$00 $00

... 62

$00 $00

$00

ReportID

$02 out

flags data

data data

... 62

data data

data

ReportID

$02 in

flags $00

$00 $00

... 62

$00 $00

$00

V 1.0.3, November 6nd 2012 for chip version V1.1.0.1