UPSD3422 datasheet(166/293 Pages) STMICROELECTRONICS

166 / 293 page

USB interface

uPSD34xx

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USB Endpoint Control Register (UCON)

The Endpoint selected by the USB Endpoint Select Register (see Table 82 on

page 165) determines the direction and FIFO (IN or OUT) that is controlled by the USB

Endpoint Control Register (see Table 83). The USB Endpoint Control Register is used

to control the selected Endpoint and provides some status about that Endpoint.

Table 83.

USB Endpoint Control Register (UCON 0F1h, Reset Value 08h)

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

–

Enable

STALL

TOGGLE

BSY

Bit

Symbol

R/W

Definition

–

Reserved

–

Reserved

–

Reserved

–

Reserved

ENABLE

R/W

Selected FIFO Enable Bit.

Note: All FIFOs for each endpoint is enabled after a reset.

2STALL

R/W

Stall Control Bit

When this bit is set, the Endpoint returns a STALL handshake whenever

it receives an IN or OUT token.

TOGGLE

Data Toggle Bit

– Endpoint IN Case

The state of this bit determines the type of data packet (0=DATA0 or

1=DATA1) that will be sent during the next IN transaction. This bit is

managed by the USB SIE. It is only toggled when an ACK is properly

received during the IN transaction. In some cases it may be necessary

for firmware to clear this bit. In this case, see the Important Notes

section at the end of this data sheet.

– Endpoint OUT Case

The state of this bit indicates the type of data packet PID that the USB

SIE expects to receive with the next OUT transaction (0=DATA0,

1=DATA1). If the Data Toggle for the next OUT transaction received is

not as expected, the USB SIE assumes the host is retransmitting the

last packet. In this case, an ACK is sent but no interrupt is generated

since the original transmission of the packet was OK. This bit is

managed by the USB SIE. It is only toggled when an OUT packet is

properly received. In some cases it may be necessary for firmware to

clear this bit. In this case, see the Important Notes section at the end of

this data sheet.

Important notes:

1. Disabling and enabling the USB SIE using the USBEN bit the UCTL

2. Revision A silicon: See the Important Notes section at the end of the

data sheet that explains the workaround for clearing this data toggle bit.

3. Revision B silicon: Disabling and Enabling the selected FIFO using

the ENABLE bit in this register clears the data toggle bit for the selected

endpoint's FIFO.

UPSD3422 Datasheet(PDF) 166 Page - STMicroelectronics

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