Rainbow Electronics AT89C51SND1C - Manual (Page 99)

99
AT8xC51SND1C
4109E–8051–06/03
Registers Table 90. USBCON Register
USBCON (S:BCh) – USB Global Control Register
Reset Value = 0000 0000b
7 6 5 4 3 2 1 0
USBE SUSPCLK SDRMWUP - UPRSM RMWUPE CONFG FADDEN
Bit
Number
Bit
Mnemonic Description
7 USBE
USB Enable Bit
Set this bit to enable the USB controller.
Clear this bit to disable and reset the USB controller, to disable the USB
transceiver an to disable the USB controllor clock inputs.
6 SUSPCLK
Suspend USB Clock Bit
Set to disable the 48 MHz clock input (Resume Detection is still active).
Clear to enable the 48 MHz clock input.
5 SDRMWUP
Send Remote Wake-Up Bit
Set to force an external interrupt on the USB controller for Remote Wake UP
purpose.
An upstream resume is send only if the bit RMWUPE is set, all USB clocks are
enabled AND the USB bus was in SUSPEND state for at least 5 ms. See
UPRSM below.
Cleared by software.
4 -
Reserved
The value read from this bit is always 0. Do not set this bit.
3 UPRSM
Upstream Resume Bit (read only)
Set by hardware when SDRMWUP has been set and if RMWUPE is enabled.
Cleared by hardware after the upstream resume has been sent.
2 RMWUPE
Remote Wake-Up Enable Bit
Set to enabled request an upstream resume signaling to the host.
Clear after the upstream resume has been indicated by RSMINPR.
Note: Do not set this bit if the host has not set the DEVICE_REMOTE_WAKEUP
feature for the device.
1 CONFG
Configuration Bit
This bit should be set by the device firmware after a SET_CONFIGURATION
request with a non-zero value has been correctly processed.
It should be cleared by the device firmware when a SET_CONFIGURATION
request with a zero value is received. It is cleared by hardware on hardware
reset or when an USB reset is detected on the bus (SE0 state for at least 32 Full
Speed bit times: typically 2.7
µ s).
0 FADDEN
Function Address Enable Bit
This bit should be set by the device firmware after a successful status phase of a
SET_ADDRESS transaction.
It should not be cleared afterwards by the device firmware. It is cleared by
hardware on hardware reset or when an USB reset is received (see above).
When this bit is cleared, the default function address is used (0).