ST7265X datasheet(75/166 Pages) STMICROELECTRONICS

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ST7265x

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USB INTERFACE (Cont’d)

Bits 1:0 = STAT_RX [1:0]

Status bits, for reception

transfers.

These bits contain the information about the end-

point status, as listed below:

Table 21. Reception Status Encoding

These bits are written by software. Hardware sets

the STAT_RX and STAT_TX bits to NAK when a

correct transfer has occurred (CTR=1) addressed

to this endpoint, so the software has the time to ex-

amine the received data before acknowledging a

new transaction.

Notes:

If a SETUP is received while the status is other

than DISABLED, it is acknowledged and the two

directional status bits are set to NAK by hardware.

When a STALL is answered by the USB device,

the two directional status bits are set to STALL by

hardware.

ENDPOINT

RECEPTION

(EP1RXR)

Read/Write

Reset value: 0000 0000 (00h)

This register is used for controlling Endpoint 1 re-

ception. Bits 2:0 are also reset by a USB reset, ei-

ther received from the USB or forced through the

FRES bit in the CTLR register.

Bits 7:4 Reserved, forced by hardware to 0.

Bit 3 = CTR_RX

Correct Reception Transfer.

This bit is set by hardware when a correct transfer

operation is performed in reception. This bit must

be cleared after the corresponding interrupt has

been serviced.

Bit 2 = DTOG_RX

Data Toggle, for reception

transfers.

It contains the expected value of the toggle bit

(0=DATA0, 1=DATA1) for the next data packet.

The receiver toggles DTOG_RX only if it receives

a correct data packet and the packet’s data PID

matches the receiver sequence bit.

Bits 1:0 = STAT_RX [1:0]

Status bits, for reception

transfers.

These bits contain the information about the end-

point status, as listed below:

Table 22. Reception Status Encoding:

These bits are written by software, but hardware

sets the STAT_RX bits to NAK when a correct

transfer has occurred (CTR=1) addressed to this

endpoint, so the software has the time to examine

the received data before acknowledging a new

transaction.

STAT_RX1 STAT_RX0

Meaning

DISABLED: no function can be

executed on this endpoint and

messages related to this end-

point are ignored.

STALL: the endpoint is stalled

and all reception requests re-

sult in a STALL handshake.

NAK: the endpoint is NAKed

and all reception requests re-

sult in a NAK handshake.

VALID: this endpoint is ena-

bled (if an address match oc-

curs, the USB interface

handles the transaction).

000

CTR_R

DTOG

_RX

STAT_

RX1

STAT_

RX0

STAT_RX1 STAT_RX0

Meaning

DISABLED: reception trans-

fers cannot be executed.

STALL: the endpoint is stalled

and all reception requests re-

sult in a STALL handshake.

NAK: the endpoint is naked

and all reception requests re-

sult in a NAK handshake.

VALID: this endpoint is ena-

bled for reception.

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