Rainbow Electronics AT89C5131 - Manual (Page 130)

130
AT89C5131
4136A–USB–03/03
Detach Simulation In order to be re-enumerated by the Host, the AT89C5131 has the possibility to simulate
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.
Figure 61. Example of V
REF
Connection
Figure 62. Disconnect Timing
USB Interrupt System
Interrupt System Priorities Figure 63. USB Interrupt Control System
D-
D+
D-
D+
GND
V
CC
V
REF
1.5 kW
USB-B Connector
1
2
3
4
AT89C5131
D+
D-
V
SS
V
IL
V
IHZ
(min)
Device
Disconnected
Disconnect
Detected
> = 2,5 ms
EUSB
IE1.6
EA
IE0.7
USB
Controller
IPH/L
Interrupt Enable Lowest Priority Interrupts Priority Enable
00
01
10
11
D+
D-