Semiconductor Group
7-14
1997-10-01
Interrupt System
C541U
The register EPIRn (n=0-4) contaíns USB endpoint specific interrupt request flags. This SFR is
availble for each endpoint. If a request flag in EPIRn is set, it is automatically cleared after a read
operation of the EPIRn register.
Endpoint Interrupt Request Register EPIRn, n=0-4 (Address C4H) Reset Value EPIR0 : 11H
Reset Value EPIR1 to EPIR4 : 10H
Bit
Function
ACKn
USB acknowledge
Bit ACKn=1 indicates a succesful action on the USB.
NACKn
USB not acknowledge
Bit NACK is set for all unsuccessful actions on the USB.
RLEn
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;
DNRn
Data not ready
This bit is set by hardware if the USB module requires an access to USB
memory, but no buffer is available.
NODn
No data
This bit indicates an incorrect CPU read or write access to USB memory.
EODn
End of data
During an USB read access EOD is set if the CPU has written a
programmable number of bytes in the transmit buffer. During an USB write
access EOD is set if the CPU has read a programmable number of bytes out
of the receive buffer.
SODn
Start of data
During an USB read access SOD is set if the USB has read a fixed number of
bytes from the transmit buffer. During an USB write access SOD is set if the
USB has written a fixed number of bytes to the receive buffer.
MSB
LSB
EPIRn
ACKn
NACKn
RLEn
–
DNRn
NODn
EODn
SODn
7
6
5
4
3
2
1
0
Bit No.
r
r
r
r
r
r
r
r
C4H
For accessing EPIRn, SFR EPSEL must be 0nH
.
Summary of Contents for C541U
Page 1: ... 8 LW 026 0LFURFRQWUROOHU 8VHU V 0DQXDO http www siem ens d Sem iconductor ...
Page 7: ......
Page 21: ...Semiconductor Group 2 6 1997 10 01 Fundamental Structure C541U ...
Page 37: ...Semiconductor Group 4 6 1997 10 01 External Bus Interface C541U ...
Page 133: ...Semiconductor Group 6 88 1999 04 01 On Chip Peripheral Components C541U ...
Page 163: ...Semiconductor Group 8 8 1997 10 01 Fail Safe Mechanisms C541U ...
Page 185: ...Semiconductor Group 10 14 1997 10 01 OTP Memory Operation C541U ...