H8SSLASH2218 datasheet(578/750 Pages) RENESAS

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Section 14 Universal Serial Bus (USB)

Rev.6.00 Jun. 03, 2008 Page 530 of 698

REJ09B0074-0600

14.8.10

Level Shifter for VBUS and

IRQx Pins

The VBUS and

IRQx pins of this USB module must be connected to the USB connector’s VBUS

pin via a level shifter. This is because the USB module has a circuit that operates by detecting

USB cable connection or disconnection.

Even if the power of the device incorporating this USB module is turned off, 5-V power is applied

to the USB connector’s VBUS pin while the USB cable is connected to the device set. To protect

the LSI from destruction, use a level shifter such as the HD74LV-A Series, which allows voltage

application to the pin even when the power is off.

14.8.11

USB Endpoint Data Read and Write

To write data to an USB endpoint data register (UEDR0i, UEDR1, or UEDR3) on the transmit side

using a CPU word or longword transfer instruction, the size of data to be written must be smaller

than the size of data that is to be transmitted.

For example, when 7-byte data is transferred to the host, 8-byte data is sent to the host if data is

written twice by the longword transfer instructions or if data is written four times by the word

transfer instructions. To write 7-byte data correctly, data must be written once by a longword

transfer instruction, once by a word transfer instruction, and once by a byte transfer instruction, or

data must be written three times by a word transfer instruction and once by a byte transfer

instruction.

To read data from the USB endpoint data register (UEDR0o or UEDR2) on the receive side, the

correct size of data must be read. In this case, the data size is specified by the USB endpoint

receive size register (UESZ0o or UESZ2).

To execute DMA transfer on data in the USB endpoint data register using the on-chip DMAC,

byte transfer musts be used. In word transfer, odd-byte data cannot be transferred. Word transfer is

thus disabled.

14.8.12

Restrictions on Entering and Canceling Power-Down Mode

Before entering the power-down mode, set the USB module stop 2 state. The UDC core must not

be reset.

To access the USB module after canceling power-down mode, cancel the USB module stop 2 state

and wait for the USB operating clock (48 MHz) stabilization time.

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