Datasheet

Byte Data Link Controller Module
Transmitting An In-Frame Response (IFR)
MC9S12DP256 — Revision 1.1
Byte Data Link Controller Module
Transmitting An In-Frame Response (IFR)
The BDLC can be used to transmit all four types of In-Frame Response
(IFR) which are defined in SAE J1850. A very brief definition of each IFR
type is given below. For a more detailed description of each, refer the
SAE J1850 document.
The explanation regarding IFR support by the BDLC which assumes the
user is familiar with the use of IFRs as defined in SAE J1850, and
understands the message header bit encoding and normalization bit
formats which are used with the different types of IFRs. For more
information on this, refer to the SAE J1850 document.
IFR Types
Supported by the
BDLC
SAE J1850 defines four distinct types of IFR. The first (and most basic)
IFR is Type 0, or no IFR. IFR types 1, 2 & 3 are each made up of one or
more bytes and, depending upon the type used, may be followed by a
CRC byte. The BDLC is designed to allow the user to transmit and
receive all types of SAE J1850 IFRs, but only the network framing/error
checking/bus acquisition duties are performed by the BDLC. The user is
responsible for determining the type of IFR to be transmitted, the number
of retries to be made (if allowed), and the allowable number of bytes to
be transmitted.
IFR Type 0: No
Response
The most basic type of IFR is no IFR. The Type 0 IFR, as defined in SAE
J1850, is no response. The EOD and EOF symbols follow directly after
the CRC byte at the end of the message frame being transmitted. This
type of IFR is, of course, inherently supported by the BDLC with no
additional user intervention required.
IFR Type 1: Single
Byte from a Single
Responder
SAE J1850 defines the Type 1 IFR as a single byte from a single
receiver. This type of IFR is used to acknowledge to the transmitter that
the message frame was transmitted successfully on the network, and
that at least one receiver received it correctly. A Type 1 IFR generally
consists of the physical node ID of the receiver responding to the
message, with no CRC byte appended. This type of response is used for
Broadcast-type messages, where there may be several intended
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