sc9s12hy64j0vllr Freescale Semiconductor, Inc, sc9s12hy64j0vllr Datasheet - Page 179

• Manufacturer Part Number: sc9s12hy64j0vllr
• Description: S12 Microcontrollers Mcu 16-bit Hcs12 Cisc 32kb Flash 5v Tray
• Manufacturer: Freescale Semiconductor, Inc

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.
The hardware handshake protocol is enabled by the ACK_ENABLE and disabled by the ACK_DISABLE
BDM commands. This provides backwards compatibility with the existing POD devices which are not
able to execute the hardware handshake protocol. It also allows for new POD devices, that support the
hardware handshake protocol, to freely communicate with the target device. If desired, without the need
for waiting for the ACK pulse.
The commands are described as follows:
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 5.4.3, “BDM Hardware Commands”
for more information on the BDM 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
Freescale Semiconductor
(Target MCU)
Drives SYNC
To BKGD Pin
•
•
Target MCU
BDM Clock
BKGD Pin
BKGD Pin
Drives to
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.
Host
This information is being provided so that the MCU integrator will be aware
that such a conflict could occur.
Figure 5-13. ACK Pulse and SYNC Request Conflict
MC9S12HY/HA-Family Reference Manual, Rev. 1.04
Host SYNC Request Pulse
ACK Pulse
16 Cycles
Host and
Target Drive
to BKGD Pin
At Least 128 Cycles
and
NOTE
Section 5.4.4, “Standard BDM Firmware Commands”
Electrical Conflict
High-Impedance
Background Debug Module (S12SBDMV1)
Speedup Pulse
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