MAC7200 datasheet(224/976 Pages) FREESCALE

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External Signal Description

MAC7200 Microcontroller Family Reference Manual, Rev. 2

146

Freescale Semiconductor

NOTE

The “End Message” state may also indicate the end of a variable-length

packet as well as the end of the message when using the two-pin option.

11.9.4

Rules for Output Messages

ARM7 based Class 3 compliant embedded processors must provide messages via the auxiliary port in a

consistent manner as described below:

•

A variable-sized packet within a message must end on a port boundary.

•

Whenever a variable-length packet is sized such that it does not end on a port boundary, it is

necessary to extend and zero fill the remaining bits after the highest-order bit so that it can end on

a port boundary.

For example, if the MDO port is 2 bits wide, and the unique portion of an indirect branch address

is 5 bits, then the remaining 1 bit of MDO must be packed with a 0.

•

A variable-sized packet may start within a port boundary only when following a fixed length

packet. (If two variable-sized packets end and start on the same clock, it is impossible to know

which bits are from the last packet and which bits are from the next packet.

11.9.5

Examples

The following are examples of Program Trace Messages.

Idle

Normal

Transfer

End

Message

MSEO=11

MSEO=00

MSEO=01

MSEO=00

MSEO=11

MDO: Invalid

MSEO=01

End

Packet

=11

MSEO=11

MSEO=10

Start

Message

MSEO=01

MSEO=10

Figure 11-3. Two Pin MSEO Transfers

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