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(3) IN_SUSPEND
When the USB controller enters this state, the USBCTL.NONJDETEN bit is automatically set by the hardware
to enable the function for detecting bus state transitions from FS-J (Suspend) to Reset or Resume. If a such bus
transition is detected, the USBSIEINTF.NONJIF bit is set to indicate that the host requests to return from Sus-
pend and a NonJ interrupt occurs when the USBSIEINTE.NONJIE and USBMAININTE.SIEIE bits = 1. In this
case, the USBCTL.NONJDETEN bit should be cleared. This puts the USB controller into the CHK_EVENT
state.
To resume from Suspend with a remote wake-up, set the USBCTL.WAKEUP bit in this state and output the re-
sume signal (FS-K) for 1 to 15 ms.
(4) CHK_EVENT
In the CHK_EVENT state, the USB controller checks the USB signal and determines that the state is Resume if
FS-K is detected, and that it is Reset if SE0 is detected. When determined to be Reset, the USBSIEINTF.RESE-
TIF bit is set.
Note that software should terminate this auto-negotiation function in any state as soon as the USB cable is un-
plugged, as the USB controller does not consider the implication of USB cable disconnection.
22.5.8 Description by Negotiation Function
Detecting Suspend
When the USBCTL.BUSDETDIS bit is cleared to 0, the USB controller automatically performs the following
Suspend detection sequence.
1. Checks that there is no data transmission/reception (the USBSTAT.LINESTAT[1:0] bits = 0x01 (J) is con-
tinuously detected) for 3 ms or longer (T
2. Sets the USBSIEINTF.SUSPENDIF bit if the USBSTAT.LINESTAT[1:0] bits = 0x01 (J) is detected at T
3. Outputs an interrupt request to the CPU if the USBSIEINTE.SUSPENDIE and USBMAININTE.SIEIE bits
are both set to 1.
When the USBSIEINTF.SUSPENDIF bit has been set (when an interrupt has occurred), perform the processing
shown below via software.
1. Set the USBCTL.BUSDETDIS bit to 1.
2. Start a Snooze processing before reaching T
Figure 22.5.8.1 shows the operation between Suspend detection and transition to Snooze.
Time
USBSIEINTF.SUSPENDIF
SNOOZE signal*
USBCTL.BUSDETDIS
USBSTAT.LINESTATE[1:0]
USB_DP/USB_DM pins
Internal USB clock
S1C31W74 TECHNICAL MANUAL
(Rev. 1.1)
) using an internal timer.
1
4
T
0
Last activity
Fully meet USB 2.0 required frequency
* The SNOOZE signal should be controlled using the USBMISCCTL.USBSNZ bit.
Figure 22.5.8.1 Suspend Timing
Seiko Epson Corporation
22 USB 2.0 FS DEVICE CONTROLLER (USB, USBMISC)
(Disable Reset/Suspend detection)
(refer to Section 22.5.10, "Snooze").
T
T
T
1
2
3
T
T
4
5
J state
J state
.
2
22-15
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