Background Debug Module (S12SBDMV1)
MC9S12VRP Family Reference Manual Rev. 1.3
NXP Semiconductors
187
Since the host knows the target serial clock frequency, the SYNC command (used to abort a command)
does not need to consider the lower possible target frequency. In this case, the host could issue a SYNC
very close to the 128 serial clock cycles length. Providing a small overhead on the pulse length in order to
assure the SYNC pulse will not be misinterpreted by the target. See
Section 5.4.9, “SYNC — Request
.
shows a SYNC command being issued after a READ_BYTE, which aborts the READ_BYTE
command. Note that, after the command is aborted a new command could be issued by the host computer.
Figure 5-12. ACK Abort Procedure at the Command Level
NOTE
does not represent the signals in a true timing scale
shows a conflict between the ACK pulse and the SYNC request pulse. This conflict could
occur if a POD device is connected to the target BKGD pin and the target is already in debug active mode.
Consider that the target CPU is executing a pending BDM command at the exact moment the POD is being
connected to the BKGD pin. In this case, an ACK pulse is issued along with the SYNC command. In this
case, there is an electrical conflict between the ACK speedup pulse and the SYNC pulse. Since this is not
a probable situation, the protocol does not prevent this conflict from happening.
Figure 5-13. ACK Pulse and SYNC Request Conflict
READ_BYTE
READ_STATUS
BKGD Pin
Memory Address
New BDM Command
New BDM Command
Host Target
Host Target
Host Target
SYNC Response
From the Target
(Out of Scale)
BDM Decode
and Starts to Execute
the READ_BYTE Command
READ_BYTE CMD is Aborted
by the SYNC Request
(Out of Scale)
BDM Clock
(Target MCU)
Target MCU
Drives to
BKGD Pin
BKGD Pin
16 Cycles
Speedup Pulse
High-Impedance
Host
Drives SYNC
To BKGD Pin
ACK Pulse
Host SYNC Request Pulse
At Least 128 Cycles
Electrical Conflict
Host and
Target Drive
to BKGD Pin
Summary of Contents for MC9S12VRP64
Page 16: ...MC9S12VRP Family Reference Manual Rev 1 3 16 NXP Semiconductors ...
Page 46: ...Device Overview S12VRP Series MC9S12VRP Family Reference Manual Rev 1 3 46 NXP Semiconductors ...
Page 236: ...S12S Debug Module S12DBGV2 MC9S12VRP Family Reference Manual Rev 1 3 236 NXP Semiconductors ...
Page 244: ...Interrupt Module S12SINTV1 MC9S12VRP Family Reference Manual Rev 1 3 244 NXP Semiconductors ...
Page 358: ...Timer Module TIM16B2CV3 MC9S12VRP Family Reference Manual Rev 1 3 358 NXP Semiconductors ...
Page 436: ...Supply Voltage Sensor BATSV2 MC9S12VRP Family Reference Manual Rev 1 3 436 NXP Semiconductors ...
Page 528: ...NVM Electrical Parameters MC9S12VRP Family Reference Manual Rev 1 3 528 NXP Semiconductors ...
Page 530: ...Package Information MC9S12VRP Family Reference Manual Rev 1 3 530 NXP Semiconductors ...
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