Datasheet

Background Debug Module (BDM)
Operation
MC9S12DP256 — Revision 1.1
Background Debug Module (BDM)
The tag follows program information as it advances through the
instruction queue. When a tagged instruction reaches the head of the
queue, the CPU enters active BDM rather than executing the instruction.
NOTE: Tagging is disabled when BDM becomes active and BDM serial
commands are not processed while tagging is active.
Executing the BDM TAGGO command configures two system pins for
tagging. The TAGLO
signal shares a pin with the LSTRB signal, and the
TAGHI
signal shares a pin with the BKGD signal.
Table 123 shows the functions of the two tagging pins. The pins operate
independently, that is, the state of one pin does not affect the function of
the other. The presence of logic level 0 on either pin at the fall of the
external clock (ECLK) performs the indicated function. High tagging is
allowed in all modes. Low tagging is allowed only when low strobe is
enabled (LSTRB is allowed only in wide expanded modes and emulation
expanded narrow mode).
Table 123 Tag Pin Function
TAGHI TAGLO Tag
1 1 No tag
1 0 Low byte
0 1 High byte
0 0 Both bytes
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