Semiconductor Group
7-12
1997-10-01
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
Function
SE0I
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.
DAI
Device attached interrupt
Bit DAI is automatically set after detection of the USB device being attached to
the USB bus.
DDI
Device detached interrupt
Bit DDI is automatically set after detection of the device being detached from the
USB bus.
SBI
Suspend begin interrupt
Bit SBI is automatically set when the suspend mode is entered.
SEI
Suspend end interrupt
Bit SBI is automatically set when the suspend mode is left.
STI
Status interrupt
Bit STI is set if the host requests a status transfer and the device answers with
NACK.
SUI
Setup interrupt
Bit SUI is automatically set after a successful reception of a setup packet.
SOFI
Start of frame
Bit SOF is automatically set after detection of a start of frame packet on the USB.
MSB
LSB
Bit No.
DIRR
SE0I
DAI
DDI
SBI
SEI
STI
SUI
SOFI
C4H
7
6
5
4
3
2
1
0
For accessing DIRR, SFR EPSEL must be 80H
.
Содержание C541U
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