2–2

CODE

XDATA

0000

8k ROM

1FFF

FD80

512 Bytes

RAM

FF80

MMR

FFFF

Figure 2–2. MCU Memory Map (ROM Version)

2.2

Miscellaneous Registers

2.2.1

TUSB3210 Boot Operation

Since the code-space is in RAM (with the exception of the boot ROM), the TUSB3210 firmware must be loaded from

bus, or the host may be used via the USB. On device reset, the SDW bit (in ROM register) and CONT bit in USB

Control Register (USBCTL) will be cleared. This will configure the memory space to boot mode (see memory map)

and will keep the device disconnected from the host.

The first instruction will be fetched from location 0000 (which is in the 6k-ROM). The 8k-RAM will be mapped to XDATA

space (location 0000h). MCU will execute a read from an external EEPROM and test to see if it contains the code

(test for boot signature). If it contains the code, MCU will read from EEPROM and write to the 8k-RAM in XDATA

space. If not, MCU will proceed to boot from USB.

Once the code is loaded, the MCU will set SDW to 1. This will switch the memory map to normal mode, i.e. the 8k-RAM

will be mapped to code space, and the MCU will start executing from location 0000h. Once the switch is done, the

MCU will set CONT to 1 (in USBCTL register) This will connect the device to the USB bus, resulting in the normal

USB device enumeration.