Cypress CY7C68013 USB Boot Methods, ReNumeration, Bus-powered Applications, Interrupt System

CY7C68013A, CY7C68014A

CY7C68015A, CY7C68016A

Table 1. Special Function Registers

x	8x	9x	Ax	Bx	Cx	Dx	Ex	Fx
0	IOA	IOB	IOC	IOD	SCON1	PSW	ACC	B
1	SP	EXIF	INT2CLR	IOE	SBUF1
2	DPL0	MPAGE	INT4CLR	OEA
3	DPH0			OEB
4	DPL1			OEC
5	DPH1			OED
6	DPS			OEE
7	PCON
8	TCON	SCON0	IE	IP	T2CON	EICON	EIE	EIP
9	TMOD	SBUF0
A	TL0	AUTOPTRH1	EP2468STAT	EP01STAT	RCAP2L
B	TL1	AUTOPTRL1	EP24FIFOFLGS	GPIFTRIG	RCAP2H
C	TH0	reserved	EP68FIFOFLGS		TL2
D	TH1	AUTOPTRH2		GPIFSGLDATH	TH2
E	CKCON	AUTOPTRL2		GPIFSGLDATLX
F		reserved	AUTOPTRSET-UP	GPIFSGLDATLNOX

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]

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)

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 automati- cally 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 onto its stack then jumps to the address 0x0043 where it expects to find a “jump” instruction to the USB Interrupt service routine.

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.

Document #: 38-08032 Rev. *L Page 4 of 62

[+] Feedback