AT43USB325E-AU Atmel, AT43USB325E-AU Datasheet - Page 92

• Manufacturer Part Number: AT43USB325E-AU
• Description: IC USB KEYBOARD CTRLR 64LQFP
• Manufacturer: Atmel
• Series: AVR®r

Specifications of AT43USB325E-AU

• Applications: Keyboard Controller
• Core Processor: AVR
• Program Memory Type: SRAM (16 kB)
• Controller Series: AT43USB
• Ram Size: 512 x 8
• Interface: SPI, 3-Wire Serial
• Number Of I /o: 42
• Voltage - Supply: 4.4 V ~ 5.25 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 64-LQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

8.5
8.5.1
8.5.2
8.5.3
92
Suspend and Resume
AT43USB325
Global Resume
Remote Wakeup
Selective Suspend and Resume
The AT43USB325 enters suspend only when requested by the USB host through bus inactivity
for at least 3 ms. The USB hardware would detect this request, sets the GLB_SUSP bit of
SPRSR, Suspend/Resume Register, and interrupts the microcontroller if the interrupt is enabled.
The microcontroller should shut down any peripheral activity and enter the Power Down mode
by setting the SE and SM bits of MCUCR and then executes the SLEEP instruction. The USB
hardware shuts off the oscillator and PLL.
Global resume is signaled by a J to K state change on Port0. The USB hardware enables the
oscillator/PLL, propagates the RESUME signaling, and sets the RSM bit of the SPRSR, which
generates an interrupt. The microcontroller starts executing where it left off and services the
interrupt. As part of the ISR, the firmware clears the GLB_SUSP bit.
While the AT43USB325 is in global suspend, resume signaling is also possible through remote
wakeup if the remote wakeup feature is enabled. Remote wakeup is defined as a port connect,
port disconnect or resume signaling received at a downstream port or, in case of the embedded
function, through an external interrupt.
A remote wakeup initiated at a downstream port is similar in many respects to a global resume.
The USB hardware enables the oscillator/PLL, propagates the RESUME signaling, and sets the
RSM bit of the SPRSR which generates an interrupt. The microcontroller starts executing where
it left off and services the interrupt. As part of the ISR, the firmware clears the GLB_SUSP bit.
A remote wakeup from the embedded function is initiated through INT0 or the external interrupt,
INT1, which enables the oscillator/PLL and the USB hardware. The USB hardware drives
RESUME signaling and sets the FRMWUP and RSM bits of SPRSR which generates an inter-
rupt to the microcontroller. The microcontroller starts executing where it left off and services the
interrupt. As part of the ISR, the firmware clears the GLB SUSP bit.
At completion of RESUME signaling, the USB hardware sets the Port Suspend Status Change
bits of the Hub Port Status Change Registers.
See section on Hub Port Control Register, HPCON.
3355C–USB–4/05