Specifications

Developer’s Serial Bootloader, Rev. 13

FC protocol description

Freescale Semiconductor8

2.4 Interpreting MCU commands

After communication between MCU and PC is established, then MCU enters the main command

interpreter loop. The MCU executes simple commands to reprogram its own nonvolatile memory. The

communication is conducted on a master-slave mechanism: the PC issues the commands, the MCU

executes them and acknowledges the completion of each command either by data or single ACK character.

The minimal set of commands is composed of:

• Ident command

• Quit command

Two more basic commands are implemented for pure reprogramming:

• Erase command

• Write command

If the user needs a verification feature, one additional (read) command must be compiled into the MCU

code. This command is not required for pure reprogramming purposes (minimal configuration).

• Read command

CRC safety protocol implementation

The protocol provides option to switch on CRC safety for all messages. For CRC is used standard 16 bit

implementation CCITT16 and as reset value is used 0xFFFF.

Example value for erase command:

'E'-1byte - 0x45

'start address' - 2 bytes - 0x1234

'CRC - 2 bytes' - 0x2907

Figure 6. Typical command and response

2.4.1 Ident command

The ident command (coded as ‘I’, $49) has no additional fields.

COMMAND ADDRESS

DATA TO MCU

DATA FROM MCU

* Dashed fields are not always implemented, data from the MCU may contain only an ACK character instead.

PC TO MCU COMMAND

MCU TO PC RESPONSE

LENGTH

CRC