USB 2.0 Hi-Speed 3-Port Hub Controller Optimized for Portable Applications
Datasheet
Chapter 7 Device Interfaces
The USB3813 provides multiple interfaces for configuration and external memory access. This chapter
details the various device interfaces and their usage.
Note: For information on device configuration, refer to Chapter 6, "Device Configuration," on page 24.
7.1
SPI Interface
The device is capable of code execution from an external SPI ROM. On power up, the firmware looks
for an external SPI flash device that contains a valid signature of 2DFU (device firmware upgrade)
beginning at address 0xFFFA. If a valid signature is found, then the external ROM is enabled and the
code execution begins at address 0x0000 in the external SPI device. If a valid signature is not found,
then execution continues from internal ROM. The following sections describe the interface options to
the external SPI ROM.
The SPI interface is always enabled after reset. It can be disabled by setting the SPI_DISABLE bit in
the UTIL_CONFIG1 register.
Note: For SPI timing information, refer to Section 9.5.7, "SPI Timing," on page 64.
7.1.1
Operation of the Hi-Speed Read Sequence
The SPI controller will automatically handle code reads going out to the SPI ROM address. When the
controller detects a read, the controller drives SPI_CE_N low, and outputs 0x0B, followed by the 24-
bit address. The SPI controller outputs a DUMMY byte. The next eight clocks will clock-in the first byte.
When the first byte is clocked-in, a ready signal is sent back to the processor, and the processor gets
one byte.
After the processor gets the first byte, its address will change. If the address is one more than the last
address, the SPI controller will clock out one more byte. If the address is anything other than one more
than the last address, the SPI controller will terminate the transaction by driving SPI_CE_N high. As
long as the addresses are sequential, the SPI Controller will continue clocking data in.
SPI_CE_N
80
55 56
63 64
71 72
0
4
5
6
7 8
15 16
23 24
31 32
39 40
47 48
1
2
3
SPI_CLK
SPI_DO
X
ADD.
ADD.
ADD.
0B
MSB
MSB
N
N+1
N+2
N+3
N+4
HIGH IMPEDANCE
DOUT
DOUT
DOUT
DOUT
DOUT
SPI_DI
MSB
Figure 7.1 SPI Hi-Speed Read Sequence
Revision 1.0 (06-17-13)
28
SMSC USB3813
DATASHEET
SMSC [ SMSC CORPORATION ]
