CY7C68013A, CY7C68014A
CY7C68015A, CY7C68016A
Document #: 38-08032 Rev. *N
Page 4 of 62
3.5 USB Boot Methods
During the power up sequence, internal logic checks the I2C port
for the connection of an EEPROM whose first byte is either 0xC0
or 0xC2. If found, it uses the VID/PID/DID values in the EEPROM
in place of the internally stored values (0xC0), or it boot-loads the
EEPROM contents into internal RAM (0xC2). If no EEPROM is
detected, FX2LP enumerates using internally stored descriptors.
The default ID values for FX2LP are VID/PID/DID (0x04B4,
0x8613, 0xAxxx where xxx = Chip revision).[2]
3.6 ReNumeration
Because the FX2LP’s configuration is soft, one chip can take on
the identities of multiple distinct USB devices.
When
first
plugged
into
USB,
the
FX2LP
enumerates
automatically and downloads firmware and USB descriptor
tables over the USB cable. Next, the FX2LP enumerates again,
this time as a device defined by the downloaded information.
This patented two step process called ReNumeration
™ happens
instantly when the device is plugged in, without a hint that the
initial download step has occurred.
Two control bits in the USBCS (USB Control and Status) register,
control the ReNumeration process: DISCON and RENUM. To
simulate a USB disconnect, the firmware sets DISCON to 1. To
reconnect, the firmware clears DISCON to 0.
Before reconnecting, the firmware sets or clears the RENUM bit
to indicate whether the firmware or the Default USB Device
handles device requests over endpoint zero: if RENUM = 0, the
Default USB Device handles device requests; if RENUM = 1, the
firmware services the requests.
3.7 Bus-Powered Applications
The FX2LP fully supports bus powered designs by enumerating
with less than 100 mA as required by the USB 2.0 specification.
3.8 Interrupt System
3.8.1 INT2 Interrupt Request and Enable Registers
FX2LP implements an autovector feature for INT2 and INT4.
There are 27 INT2 (USB) vectors, and 14 INT4 (FIFO/GPIF)
vectors. See EZ-USB Technical Reference Manual (TRM) for
more details.
3.8.2 USB Interrupt Autovectors
The main USB interrupt is shared by 27 interrupt sources. To
save the code and processing time that is required to identify the
individual USB interrupt source, the FX2LP provides a second
level of interrupt vectoring, called Autovectoring. When a USB
interrupt is asserted, the FX2LP pushes the program counter to
its stack, and then jumps to the address 0x0043 where it expects
to find a “jump” instruction to the USB Interrupt service routine.
Table 1. Special Function Registers
x
8x
9x
Ax
Bx
Cx
Dx
Ex
Fx
0
IOA
IOB
IOC
IOD
SCON1
PSW
ACC
B
1SP
EXIF
INT2CLR
IOE
SBUF1
2DPL0
MPAGE
INT4CLR
OEA
3DPH0
OEB
4
DPL1
OEC
5
DPH1
OED
6
DPS
OEE
7PCON
8
TCON
SCON0
IE
IP
T2CON
EICON
EIE
EIP
9
TMOD
SBUF0
ATL0
AUTOPTRH1
EP2468STAT
EP01STAT
RCAP2L
BTL1
AUTOPTRL1
EP24FIFOFLGS
GPIFTRIG
RCAP2H
CTH0
reserved
EP68FIFOFLGS
TL2
DTH1
AUTOPTRH2
GPIFSGLDATH
TH2
E
CKCON
AUTOPTRL2
GPIFSGLDATLX
F
reserved
AUTOPTRSET-UP
GPIFSGLDATLNOX
Table 2. Default ID Values for FX2LP
Default VID/PID/DID
Vendor ID
0x04B4
Cypress Semiconductor
Product ID
0x8613
EZ-USB FX2LP
Device release
0xAnnn
Depends on chip revision
(nnn = chip revision where first
silicon = 001)
Note
2. The I2C bus SCL and SDA pins must be pulled up, even if an EEPROM is not connected. Otherwise this detection method does not work properly.
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