Section 3. transport frame types, I-frames, Pcb of i-frames – MagTek MCP User Manual

Page 13: Frame type (ft), Edc type (et), Chain indicator (ci)

SECTION 3. TRANSPORT FRAME TYPES

I-FRAMES

This section defines the I-frames used in the MCP communications protocol. An I-frame
(information frame) carries an application message in the data field. Application messages are
transparent to this protocol. Application messages are outside the scope of this document. This
section defines the PCB and data fields of the I-frame.

PCB of I-frames

Below is the diagram of the PCB field in the frame header of I-frames:

7 6 5 4 3 2 1 0

FT FT

0 0

ET ET CI RFU

N(S)

N(R)

MSB

LSB

• FT

Frame Type (2 bits) = 00

• ET

EDC Type (2 bits)

• CI

Chain indicator (1 bit)

• N(S)

Send sequence number (1 bit)

• N(R)

Receive sequence number (1 bit)

Frame Type (FT)

The I-frame is designated as frame type 00 (two most significant bits in PCB).

EDC Type (ET)

Error detection code used for the whole frame. The following table defines the possible values:

Value Definition

00 No

EDC

16-bit CRC (Cyclic Redundancy Check)

8-bit LRC (Longitudinal Redundancy Check)

Reserved for future use

Chain Indicator (CI)

The chain indicator is not currently supported and must be set to zero.