Freescale Semiconductor HCS08 Series, Reference Manual

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Chapter 4 Memory
MC9S08JS16 MCU Series Reference Manual, Rev. 4
44 Freescale Semiconductor
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When security is enabled, the RAM is considered a secure memory resource and is not accessible through
BDM or through code executing from non-secure memory. See
Section 4.7, “Security ,” for a detailed
description of the security feature.
4.4 USB RAM
USB RAM is discussed in detail in Chapter 15, “Universal Serial Bus Device Controller (S08USBV1) .”
4.5 Bootloader ROM
The Bootloader ROM holds code that is used to erase and program flash memory. The Bootloader ROM
provides quick and reliable flash erase and program procedures from a USB host such as a personal
computer (PC).
Freescale provides a PC GUI (Graphic User Interface) that can communicate with bootloader in ROM via
USB interface (PC as a host USB device).
Working with the PC GUI, the user can:
• Mass erase entire flash array
• Partial erase flash array— erase all flash blocks except for the first 1 KB of flash
• Program flash
• Reset MCU
NOTE
If bootloader function is used, the MCU supply voltage must be above 4 V.
The internal USB 3.3 V voltage regulator will be enabled when entering
bootloader mode.
NOTE
USB bootloader requires an external oscillator which must be at 2 MHz,
4 MHz, 6 MHz, 8 MHz, 12 MHz, or 16 MHz. Bootloader code can identify
the external oscillator automatically. If the bootloader is not used, there are
no such restrictions.
NOTE
The USB descriptors for bootloader are fixed: VID is 0x15A2, PID is
0x0038. The user’s application can use its own descriptors.
4.5.1 External Signal Description
The BLMS pin of bootloader ROM decides whether the MCU will enter bootloader mode directly during
power-on reset. This pin is only examined during Power-On Reset (POR).
The signal properties of bootrom are shown in Table 4-5 .