MM912H634CV1AER2 Freescale Semiconductor, MM912H634CV1AER2 Datasheet - Page 195

• Manufacturer Part Number: MM912H634CV1AER2
• Description: 64KS12 LIN2xLS/HS Isense
• Manufacturer: Freescale Semiconductor
• Series: -r

Specifications of MM912H634CV1AER2

• Applications: Automotive
• Core Processor: HCS12
• Program Memory Type: FLASH (64 kB)
• Controller Series: HCS12
• Ram Size: 6K x 8
• Interface: LIN
• Number Of I /o: -
• Voltage - Supply: 5.5 V ~ 27 V
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: Surface Mount
• Package / Case: 48-LQFP Exposed Pad
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

The default state of the BDM after reset is hardware handshake protocol disabled.
All the read commands will ACK (if enabled) when the data bus cycle has completed and the data is then ready for reading out
by the BKGD serial pin. All the write commands will ACK (if enabled) after the data has been received by the BDM through the
BKGD serial pin and when the data bus cycle is complete. See
Section 4.31.4.4, “Standard BDM Firmware Commands”
The ACK_ENABLE sends an ACK pulse when the command has been completed. This feature could be used by the host to
evaluate if the target supports the hardware handshake protocol. If an ACK pulse is issued in response to this command, the host
knows that the target supports the hardware handshake protocol. If the target does not support the hardware handshake protocol
the ACK pulse is not issued. In this case, the ACK_ENABLE command is ignored by the target since it is not recognized as a
valid command.
The BACKGROUND command issues an ACK pulse when the CPU changes from normal to background mode. The ACK pulse
related to this command could be aborted using the SYNC command.
The GO command issues an ACK pulse when the CPU exits from background mode. The ACK pulse related to this command
could be aborted using the SYNC command.
The GO_UNTIL(171) command is equivalent to a GO command with exception that the ACK pulse, in this case, is issued when
the CPU enters into background mode. This command is an alternative to the GO command and should be used when the host
wants to trace if a breakpoint match occurs and causes the CPU to enter active background mode. Note that the ACK is issued
whenever the CPU enters BDM, which could be caused by a breakpoint match or by a BGND instruction being executed. The
ACK pulse related to this command could be aborted using the SYNC command.
The TRACE1 command has the related ACK pulse issued when the CPU enters background active mode after one instruction
of the application program is executed. The ACK pulse related to this command could be aborted using the SYNC command.
4.31.4.9
The SYNC command is unlike other BDM commands because the host does not necessarily know the correct communication
speed to use for BDM communications until after it has analyzed the response to the SYNC command. To issue a SYNC
command, the host should perform the following steps:
Upon detecting the SYNC request from the host, the target performs the following steps:
The host measures the low time of this 128 cycle SYNC response pulse and determines the correct speed for subsequent BDM
communications. Typically, the host can determine the correct communication speed within a few percent of the actual target
speed and the communication protocol can easily tolerate speed errors of several percent.
As soon as the SYNC request is detected by the target, any partially received command or bit retrieved is discarded. This is
referred to as a soft-reset, equivalent to a time-out in the serial communication. After the SYNC response, the target will consider
the next negative edge (issued by the host) as the start of a new BDM command or the start of new SYNC request.
Another use of the SYNC command pulse is to abort a pending ACK pulse. The behavior is exactly the same as in a regular
SYNC command. Note that one of the possible causes for a command to not be acknowledged by the target is a host-target
synchronization problem. In this case, the command may not have been understood by the target and so an ACK response pulse
will not be issued.
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ACK_ENABLE — enables the hardware handshake protocol. The target will issue the ACK pulse when a CPU
command is executed by the CPU. The ACK_ENABLE command itself also has the ACK pulse as a response.
ACK_DISABLE — disables the ACK pulse protocol. In this case, the host needs to use the worst case delay time at the
appropriate places in the protocol.
Drive the BKGD pin low for at least 128 cycles at the lowest possible BDM serial communication frequency
Drive BKGD high for a brief speedup pulse to get a fast rise time (this speedup pulse is typically one cycle of the host
clock.)
Remove all drive to the BKGD pin so it reverts to high impedance.
Listen to the BKGD pin for the sync response pulse.
Discards any incomplete command received or bit retrieved.
Waits for BKGD to return to a logic one.
Delays 16 cycles to allow the host to stop driving the high speedup pulse.
Drives BKGD low for 128 cycles at the current BDM serial communication frequency.
Drives a one-cycle high speedup pulse to force a fast rise time on BKGD.
Removes all drive to the BKGD pin so it reverts to high impedance.
SYNC — Request Timed Reference Pulse
MM912_634 Advance Information, Rev. 4.0
for more information on the BDM commands.
Section 4.31.4.3, “BDM Hardware Commands”
and
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