AT90SCR100 datasheet(160/433 Pages) ATMEL

160 / 433 page

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TPR0327AY–SMS–30Jan09

AT90SCR100

PIDs and separate data toggle sequence bits for the data transmitter and receiver. Receiver

sequence bits toggle only when the receiver is able to accept data and receives an error-free

data packet with the correct data PID. Transmitter sequence bits toggle only when the data

transmitter receives a valid ACK handshake. Data toggle synchronization is not supported for

isochronous transfers.

14.4

Attachment Procedure

This procedure must be applied in order to connect the pull-up between the USB signal D+ and

USBReg, thus identifying a Full-Speed USB device.

Even after reset, the pull-up is not connected. This operation must be controlled by the software

in order to attach the device.

We can imagine two integration scenarios for AT90SCR100:

• If the AT90SCR100 is standalone USB device Smart Card reader, then, connecting the USB

cable into a computer, for instance, will power up the AT90SCR100. After chip initialization,

PLL running, the USB module can be enabled using USBCR.USBE bit, set attachement pull-

up can also be set to make the host detect a full-speed peripheral. The host will then reset

the communication, and the FEURI interruption will trigger. A enumeration procedure can

finally go ahead naturally.

• If the AT90SCR100 can be controlled by different hosts, for example by USART and USB,

and if the host detection must be done dynamically, then a specific detection must be

initiated. After chip power up, communication modules initialisation and PLL activation, the

interruption on USART and USB (in the example) must be activated. The attachement pull-up

must be enabled. Then, the first interruption (USBPI.FEURI or USART reception) will indicate

the host communication mode. Please note that in this case, the D- line may be in High-Z

state, making the USB module consumpts until the USB module is disabled or

communication is runnning. To prevent consumption issue, a resistor or 1MegaOhm should

be place as pull-up on USB D- line.

14.5

USB Interrupts

The USB interrupt sources are split into two main families:

• The USB Protocol Interrupts (Falling Edge on USB Reset, Start Of Frame, Resume,

Suspend). They are included into the USBPI register (see “USBPI - USB Protocol Interrupt

• The USB Endpoint Interrupt (Endpoint0, 1, 2, 3, 4, 5, 6 and 7). They are included into the

USBEI register (see “USBEI - USB Endpoint Interrupt Register” on page 166 for further

details). This register only indicates which endpoint of the eight holds the source of the

interruption. The source of the interruption can then be retrieved by checking the register

USBCSEX corresponding to the endpoint (see “USBCSEX - USB Control And Status

The USB hardware module integrates the attachment pull-up resistors connected

between the USB D+ differential data line and the internal 3.3 V USB regulator

(USBReg).

The serial resistors required by USB certification are not embedded in the USB

hardware module. They must be added externally.

Note

AT90SCR100 Datasheet(PDF) 160 Page - ATMEL Corporation

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