Renesas CPU Board M3A-HS19 Bedienungsanleitung PDF herunterladen (Seite 15)

SH7285/SH7286 USB Function Module

USB to Serial Conversion Application Note

(2) Status Stage of the Control OUT Transfer

The USB host sends an IN token. The USB device sends a 0-byte data packet to the USB host after it receives the IN

token. Then, the USB device waits for an ACK handshake from the USB host.

When the USB function module receives the IN token, it generates the IN token receive interrupt using the EP0iTR

bit in the USBIFR0 register. When the USB function module receives an IN token although there is no valid 0-byte

data packet in the EP0iFIFO, it automatically returns a NAK handshake to the USB host. When the USB function

module has a valid 0-byte data packet in the EP0iFIFO when it receives the IN token, it sends a 0-byte data packet to

the USB host and waits for an ACK handshake from the USB host. When the USB function module receives the ACK

handshake, it generates the data transmit complete interrupt using the EP0iTS in the USBIFR0 register.

The sample program identifies the type of the interrupt while it is being processed. When it is the data transmit

complete interrupt generated by the EP0iTS in the USBIFR0 register, the sample program clears the interrupt to

complete the control transfer. When it is the IN token receive interrupt generated by the EP0iTR bit in the USBIFR0

Figure 2.12 shows an operation flowchart of the Status

Stage (Control OUT Transfer) by the sample program. When the

command is a USB communication class command

(Set Line Coding), the sample program uses a SciInit function to process the command.

IN token receive interrupt

USB Function (Hardware)

Sample Program (Software)

(USBIFR0 interrupt)

Clears EP0i transmit

complete flag

(USBIFR0/EP0iTS = 0)

Sends a 0-byte data to

the USB host

Sets the EP0i transmit

complete flag

(USBIFR0/EP0iTS = 1)

Changes the state

as WAIT

Yes

USBTRG/EP0iPKTE = 1

Clears EP0i transfer

request flag

(USBIFR0/EP0iTR = 0)

SetControlOutContents

Any valid data in the

EP0iFIFO?

EP0i transmit complete

interrupt? (USBIFR0/EP0iTS)

ActControl Out

Yes

Receives the EP0 IN token

SciInit

Disables EP0i transfer

request interrupt

(USBIER0/EP0iTR = 0)

Yes

By EP0iPKTE bit

USBIFR0/EP0iTR interrupt

Data in EP0iFIFO is

enabled by EP0iPKTE = 1.

USB command is

Set Line Coding?

Interrupt completed

Interrupt started

USBIFR0/EP0iTS

interrupt

Completed

Executes ActControlOut

function in the USBIFR0

interrupt handler.

Waits for ACK

NAK

Returns NAK to the

USB host

Initializes SCIF

Figure 2.12 Status Stage (Control OUT Transfer)

REJ05B1152-0100/Rev.1.00 May 2008 Page 15 of 35

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