C541U_99 Datasheet, PDF (145/192 Pages) Siemens Semiconductor Group – 8-BIT CMOS MICROCONTROLLER

Interrupt System
C541U
The USB device interrupt request register contains the device specific interrupt flags of the USB
module. These flags describe special events of the USB module. If a request flag is set, it is
automatically cleared after a read operation of the DIRR register. The most significant bit in GEPIR
register contains an additional device specific interrupt flag, but it needs to be cleared by software.
Special Function Registers DIRR (Address C4H)
Reset Value : 00H
Bit No. MSB
LSB
7
6
5
4
3
2
1
0
C4H SE0I DAI
DDI
SBI
SEI
STI
SUI SOFI DIRR
For accessing DIRR, SFR EPSEL must be 80H.
Bit
SE0I
DAI
DDI
SBI
SEI
STI
SUI
SOFI
Function
Single ended zero interrupt
Bit SE0I is set each time a single ended zero is detected for equal or greater than
2.5µs. EOP (2 bit times) is not detected.
Device attached interrupt
Bit DAI is automatically set after detection of the USB device being attached to
the USB bus.
Device detached interrupt
Bit DDI is automatically set after detection of the device being detached from the
USB bus.
Suspend begin interrupt
Bit SBI is automatically set when the suspend mode is entered.
Suspend end interrupt
Bit SBI is automatically set when the suspend mode is left.
Status interrupt
Bit STI is set if the host requests a status transfer and the device answers with
NACK.
Setup interrupt
Bit SUI is automatically set after a successful reception of a setup packet.
Start of frame
Bit SOF is automatically set after detection of a start of frame packet on the USB.
Semiconductor Group
7-12
1997-10-01