C541U_99 Datasheet, PDF (117/192 Pages) Siemens Semiconductor Group – 8-BIT CMOS MICROCONTROLLER

On-Chip Peripheral Components
C541U
The endpoint interrupt request register EPIRn contains the interrupt request flags of the different
endpoint specific interrupts. In general, the bits in EPIRn are reset by hardware after a EPIRn read
operation.
Endpoint Interrupt Request Register EPIRn, n=0-4 (Address C4H) Reset Value EPIR0 : 11H
Reset Value EPIR1 to EPIR4 : 10H
Bit No. MSB
LSB
7
6
5
4
3
2
1
0
C4H ACKn NACKn RLEn
–
DNRn NODn EODn SODn EPIRn
r
r
r
r
r
r
r
r
For accessing EPIRn, SFR EPSEL must be 0nH.
Bit
ACKn
NACKn
RLEn
–
DNRn
NODn
EODn
Function
USB acknowledge
Bit ACKn=1 indicates a succesful action on the USB.
USB not acknowledged
Bit NACKn is set for all unsuccessful actions on the USB.
Read length error
Bit RLEn is automatically set if the number of bytes read by the USB does not
correspond to the packet length programmed by the CPU.
Reserved bit for future use. As this bit may return nonzero value, it must be
ignored in all read accesses.
Data not ready
This bit is set by hardware if the UDC requires an access to USB memory, but no
buffer is available.
USB Read action : DNRn is set if UBF is not set.
USB Write action : DNRn is set if UBF is set.
No data
This bit indicates an incorrect CPU read or write access to USB memory. It is set
if the CPU processes a read access to an empty USB buffer or a write access to
a full buffer. NODn is also set if the direction is write (DIRn=0 for USB write
access) and the CPU tries to write to the USB memory buffer.
End of data
USB Read action : EODn is set if the CPU has written a programmable number
(MaxLen) of bytes in the transmit buffer. As a result, the buffer
is full and no more write actions from the CPU are allowed.
USB Write action: EODn is set if the CPU has read a programmable number
(USBLen) of bytes out of the receive buffer. As a result, the
buffer is empty now and no more read actions from the CPU
are allowed.
Semiconductor Group
6-72
1999-04-01