**IEEE P1451.3 Proposal**

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| Proposal Title: | Revised Frame Format                               |
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| Proposal        | 00-001                                             |
| Number:         |                                                    |
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| Revision        |                                                    |
| Number:         |                                                    |
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| Draft Version:  | D 1.06                                             |
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| Date:           | 11/28/00                                           |
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| Name:           | Larry Malchodi                                     |
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| Company:        | Boeing                                             |
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| Phone Number:   | 206 655-5695                                       |
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| Fax Number:     | 206 655-7724                                       |
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| Email Address:  | Larry.a.malchodi@boeing.com                        |
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| Proposal        | Initial Draft                                      |
| Status:         |                                                    |
|                 | Revised Draft                                      |
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|                 | [X]{.underline} Ready for Vote                     |
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| Action:         | \_\_\_ Approved                                    |
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|                 | \_\_\_ Approved with changes                       |
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|                 | \_\_\_ Rejected                                    |
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|                 | \_\_\_ Returned for revision                       |
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Summary of Issue:

The Data Link Layer Primary Frame Format contains a Format Check
Sequence and has no Frame Check Sequence. The Frame Check Sequence would
be a two byte field used to verify the integrity of the preceding 5
bytes. There are currently no provisions to verify the integrity of the
data field.

Discussion:

Proposed solution:

Modify the format of the primary frame data layer. The modification will
remove the Format Check Sequence from the format field. It will add a
Frame Check Sequence.

Draft changes:

## Data Link Layer Frame Format

There are two Data Link Layer frame formats required for the standard.
The primary frame format is shown in Figure 1. The alternate Data Link
Layer frame format is shown in Figure 2. The physical layer format
considerations are discussed in the CDMA/FDMA/TDMA section. See ??

The Bus Management Communications Channel shall only support the primary
frame format. The TBIM Communications Channel, the Data Transfer
Communications Channel and the Trigger Communications Channel may be
operated with either frame format. Different TBIMs in a system may
operate with different formats.

[Action Item FE#3 (Functional Elements) How do we allow data from
multiple Transducers in the same data frame.]{.mark}

Figure 1---Data Link Layer Primary Frame Format

![](media/image2.wmf)

Figure 2---Data Link Layer Alternate Frame Format

### Start Frame/End Frame Flag

The start frame/end frame field is a fixed pattern that is used to
detect the beginning of a transmission and to synchronize with the
incoming data, in addition it is used to indicate the end of the frame.
Different flag fields are required for the primary and the alternate
frame formats.

[Action Item FE#2 (Physical Layer Subgroup) The exact pattern will be
changed in later drafts and the start flag may be different from the
stop flag.]{.mark}

### Format Field

The main difference between the two frame formats are in these fields.

#### Format Field for the Primary Frame Format

The Format Field is made up of four distinct fields. When using this
format the syllable length shall be eight bits. No Message ID/Sequence
Number field shall be used with this frame format.

[Action Item FE-#1 - (Commands Subgroup) Define a command to be used to
set the syllable length for data transfers.]{.mark}

##### Destination/Source Address Field

This sixteen-bit field identifies the destination for transmissions from
the TBC to the TBIMs. It is the source address for transmissions from
the TBIMs to the TBC.

##### Command

This field contains the command to be executed. A frame that is intended
to transmit a command from the TBC to a transducer may or may not
contain a data field. The use of a data field in a command frame is a
function of the command. See Error: Reference source not found for more
details.

##### Data Count

This eight-bit field identifies the total number of data bytes that will
be found in the Data Field.

##### 

##### Format Field for the Alternate Frame Format

The Alternate Format Field is made up of seven distinct fields. They are
described in the following subclauses.

##### Destination Address

This sixteen-bit field is the destination address for all transmissions.

##### Source Address 

This sixteen-bit field is the source address for all transmissions.

##### Command Field

This is identical to 4.5.2.1.2.

##### Sequence Number/Message ID

This eight-bit field has a dual purpose. In some cases it is a sequence
number for frames that must be received in a particular sequence. This
is important when transmitting large blocks of data such as TEDS. In
other cases this field would be used as a message ID. This is essential
for proving that no messages have been missed and/or determining which
reply relates to a given previous message.

[Sequence number/message id field needs more thought. Should it be one
field or two?]{.mark}

##### Data Count

This sixteen-bit field shall contain the number of data bytes in the
data field of 4.5.3.

##### Format Check Sequence

This field should be the same as described in 4.5.2.1.4.

### Data Field

The data field shall contain the number of bytes of data that are
specified in the Data Count field in the Format field. A data word is
made up of one or more bytes. Words of various lengths may be used as
long as the total length of the data field is a multiple of eight bits
or is padded to meet this requirement. The length for this filed can be
from 0 to 255 bytes for the primary frame format and from 0 to 65535
bytes for the alternate frame format.

[If error detection or correction is required on the data field it will
be included as part of the data itself.]{.mark}

[The system must be capable of turning on or off the encryption in the
data fields.]{.mark}

### Frame Check

The frame check sequence is used to verify the integrity of the
transmitted frame and is required for both the primary and alternate
frame formats.

[We]{.mark} [need to decide whether]{.mark} [there]{.mark} [will be a
difference between the primary and alternate formats for this
field.]{.mark}

#### Frame Check Sequence for Primary Frame Format

[THIS FIELD MAY BE REMOVED OR ALTERED AT A LATER DATE]{.mark}

This is a required field when using the alternate Data Link Layer frame
format. The standard CRC polynomial to generate the Frame Check Sequence
field is as follows:

> X^16^+X^15^+X^2^+1.

It can detect following errors:

\- All burst errors of length \<= 16

\- All burst errors affecting an odd number of bits

\- Burst errors of length 17 with high probability

\- Burst errors of length \>17 with good probability (2x10^-10^)

The receiving device shall ignore any transmission with an incorrect
CRC.

#### Frame Check Sequence for Alternate Frame Format

[THIS FIELD MAY BE REMOVED OR ALTERED AT A LATER DATE]{.mark}

This is a required field when using the alternate Data Link Layer frame
format. The standard CRC polynomial to generate the Frame Check Sequence
field is as follows:

> X^16^+X^15^+X^2^+1.

It can detect following errors:

\- All burst errors of length \<= 16

\- All burst errors affecting an odd number of bits

\- Burst errors of length 17 with high probability

\- Burst errors of length \>17 with good probability (2x10^-10^)

The receiving device shall ignore any transmission with an incorrect
CRC.