OVERVIEW: Digital Section
1.6.8 System Memory
The following types of memories are used in i897:
1. 256MB (2Gbit) of NAND flash memory used to store unit subscriber and DSP code.
2. 128MB (1Gbit) of DDR memory used by the MCU to load code-plug information,
program the flash, and store working parameters. The DDR operates at 266MHz.
Both memories are external to the processor and are stacked in the same package.
1.6.9 USB2.0
I897 supports USB2.0 High Speed rate of 480Mbps. The file transfer throughout rate is
about 2MB/s for high speed transfers. The phone also supports USB1.1 Full Speed host.
Basically there are two USB paths in the design, high speed and full speed. Whenever a
USB data cable is connected to the phone, it defaults to High Speed mode. In this mode,
the USB interface goes through a USB2.0 Controller IC (CY7C68053-56BAXI from
Cypress). Only for flashing/programming and RS232 (Y-cable berbug) communication,
the USB interface goes through the existing Full Speed EMU IC.
There is a switch on board, controlled by Zeus, to switch between these 2 paths. For the
high speed path, the CY7C IC communicates with Zeus through a 16-bit interrupt-driven
FIFO interface. The CY7C controller has its own firmware, which is stored in the NAND
flash. During power-up, CY7C downloads its firmware from Zeus through an I2C interface.
The USB connector of the unit is a micro USB receptacle and is used to communicate to
external devices. There is no external hardware for switching from one protocol to another
because ZEUS handles the switching and line multiplexing functions internally.
The following table shows the USB connector pin assignments:
Table 1-3. USB Connector Pin Assignments
Pin Signal
1 Vbus
2 D-
3
D+
4 ID
5 GND
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