Rainbow Electronics AT89C5122 - Manual (Page 114)

114
AT8xC5122/23
4202E–SCR–06/06
Detach Simulation In order to be re-enumerated by the Host, the AT8xC5122/23 has the possibility to sim-
ulate a DETACH-ATTACH of the USB bus.
The V
REF
output voltage is between 3.0V and 3.6V. This output can be connected to the
D+ pull-up as shown in Figure 61. This output can be put in high-impedance when the
DETACH bit is set to 1 in the USBCON register. Maintaining this output in high imped-
ance for more than 3 µs will simulate the disconnection of the device. When resetting
the DETACH bit, an ATTACH is then simulated. The USB controller should be enabled
to use this feature.
Figure 61. Example of V
REF
Connection
Figure 62. Disconnect Timing
D-
D+
D-
D+
GND
VCC
V
REF
R1
USB-B Connector
1
2
3
4
R2
R3
D+
D-
V
SS
V
IL
V
IHZ(min)
Device
Disconnected
Disconnect
Detected
>= 2,5 μ s