HT82D20R/HT82D20A

Rev. 1.10

21

January 27, 2010

There are some timing constrains and usages illustrated here. By setting the MISC register, the MCU can perform read-

ing, writing and clearing actions. There are some examples shown in the following table for endpoint FIFO reading, writ-

ing and clearing.

Actions

MISC Setting Flow and Status

Read FIFO0 sequence

00H

®01H®delay of 2ms, check 41H®read* from FIFO0 register

and check if not ready (01H)

®03H®02H

Write FIFO1 sequence

0AH

®0BH®delay of 2ms, check 4BH®write* to FIFO1 register and

check if not ready (0BH)

®09H®08H

Check whether FIFO0 can be read or not

00H

®01H®delay of 2ms, check 41H (if ready) or 01H (if not

ready)

®00H

Check whether FIFO1 can be written to or not

0AH

®0BH®delay of 2ms, check 4BH (if ready) or 0BH (if not

ready)

®0AH

Write 0-sized packet sequence to FIFO 0

02H

®03H®delay of 2ms, check 43H®01H®00H

Note: *: There are 2

ms gap existing between 2 reading actions or between 2 writing actions

Register Name

R/W

Register Address

Bit7~Bit0

FIFO 0

R/W

01001000B

Data7~Data0

FIFO 1

R/W

01001001B

Data7~Data0

FIFO Register Address Table

USB Active Pipe Timing

The USB active pipe accessed by the host cannot be used by the MCU simultaneously. When the host finishes its work,

the signal, a USB_INT will be produced to tell the MCU that the pipe can be used and the acted pipe No. will be shown

in the signal, ACT_PIPE as well. The timing is illustrated in the Figure below.

USB Active Pipe Timing

U S B _ I N T

A C T _ P I P E

L a s t A c t e d P i p e

Suspend Wake-Up and Remote Wake-Up

If there is no signal on the USB bus for over 3ms, the de-

vices will go into a suspend mode. The Suspend line (bit

0 of the USC) will be set to 1 and a USB interrupt is trig-

gered to indicate that the devices should jump to the sus-

pend state.

Disable the USB clock by clearing the USBCKEN (bit3

of the SCC) to

²0². The suspend current is 1.5mA.

The user want to decrease the suspend current to about

1mA by setting the SUSP2 (bit4 of the SCC). But if the

SUSP2 is set, the user has to make sure not to enable the

LVR OPT option, otherwise the devices will be reset.

When the resume signal is sent out by the host, the de-

vices will wake-up the MCU by USB interrupt and the

Resume line (bit 3 of the USC) is set. In order to make

the device function properly, the programmer must set

the USBCKEN (bit 3 of the SCC) to 1 and clear the

SUSP2 (bit4 of the SCC). Since the Resume signal will

be cleared before the Idle signal is sent out by the host

and the Suspend line (bit 0 of the USC) is going to

²0².

So when the MCU is detecting the Suspend line (bit0 of

the USC), the Resume line should be remembered and

taken into consideration.

After finishing the resume signal, the suspend line will

go inactive and a USB interrupt is triggered. The follow-

ing is the timing diagram:

S U S P E N D

U S B R e s u m e S i g n a l

U S B _ I N T