C541U_99 Datasheet, PDF (110/192 Pages) Siemens Semiconductor Group – 8-BIT CMOS MICROCONTROLLER

On-Chip Peripheral Components
C541U
The frame number registers stores an 11-bit value which defines the number of an USB frame. The
frame number rolls over upon reaching its maximum value of 7FF_H. The FNRH/FNRL registers are
read only registers which are reset to 00H by a hardware reset.
Frame Number Register High Byte FNRH (Address C7H)
Frame Number Register Low Byte FNRL (Address C6H)
Reset Value : 00000XXXB
Reset Value : XXH
Bit No. MSB
LSB
7
6
5
4
3
2
1
0
C7H
0
0
0
0
0 FNR10 FNR9 FNR8 FNRH
r
r
r
r
r
r
r
r
C6H
FNR7
r
FNR6
r
FNR5
r
FNR4
r
FNR3
r
FNR2
r
FNR1
r
FNR0
r
FNRL
Bit
FNR10-0
Function
Frame number value
FNRH.2-.0 and FNRL.7-.0 hold the current 11-bit frame number of the latest SOF
token. FNRL holds the lowest 8 bits while FNRH holds the upper 3 bits of the
frame number.
Semiconductor Group
6-65
1999-04-01