MPC5604B/C Microcontroller Reference Manual, Rev. 8
Freescale Semiconductor 73
After the code has been downloaded to SRAM, the BAM code restores the initial device configuration and
then transfers execution to the start address of the downloaded code.
5.2.1.1 BAM resources
The BAM uses/initializes the following MCU resources:
• MC_ME and MC_CGM to initialize mode and clock sources
• FlexCAN_0, LINFlex _0 and the respective I/O pins when performing serial boot mode
• SSCM and shadow flash memory (NVPWD0,1 and NVSCC0,1) during password check
• SSCM to check the boot mode (see Table 5-5)
• 4–16 MHz fast external crystal oscillator
The system clock is selected directly from the 4–16 MHz fast external crystal oscillator. Thus, the external
oscillator frequency defines the baud rates used for serial download (see Table 5-6).
5.2.1.2 Download and execute the new code
From a high level perspective, the download protocol follows these steps:
1. Send the 64-bit password.
2. Send the start address, size of code to be downloaded (in bytes) and the VLE bit
1
.
3. Download the code.
Each step must be completed before the next step starts. After the download is complete (the specified
number of bytes is downloaded), the code executes from the start address.
Table 5-5. SSCM_STATUS[BMODE] values as used by BAM
BMODE value Corresponding boot mode
000 Reserved
001 FlexCAN_0 serial boot loader
010 LINFlex_0 (RS232 /UART) serial boot loader
011 Flash memory boot mode
100–111 Reserved
Table 5-6. Serial boot mode – baud rates
FXOSC frequency
(MHz)
LINFlex baud rate
(baud)
CAN bit rate
(bit/s)
f
FXOSC
f
FXOSC
/833 f
FXOSC
/40
8 9600 200K
12 14400 300K
16 19200 400K
1. Since the device supports only VLE code and not Book E code, this flag is used only for backward compatibility.
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