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The USCL 8-bit Prescaler Register for USB is at
E1h. The USCL should be loaded with a value that
results in a clock rate of 6MHz for the USB using
the following formula:
USB clock input =
(f
OSC
/ 2) / (Prescaler register value +1)
Where f
OSC
is the MCU clock input frequency.
Note: USB works ONLY with the MCU Clock fre-
quencies of 12, 24, or 36MHz. The Prescaler val-
ues for these frequencies are 0, 1, and 2.
Table 77. USB SFR Memory Map
SFR
Addr
Reg
Name
Bit Register Name
Reset
Value
Comments
7 6543210
E1 USCL 00
8-bit
Prescaler for
USB logic
E6 UDT1 UDT1.7 UDT1.6 UDT1.5 UDT1.4 UDT1.3 UDT1.2 UDT1.1 UDT1.0 00
USB Endpt1
Data Xmit
E7 UDT0 UDT0.7 UDT0.6 UDT0.5 UDT0.4 UDT0.3 UDT0.2 UDT0.1 UDT0.0 00
USB Endpt0
Data Xmit
E8 UISTA SUSPND — RSTF TXD0F RXD0F RXD1F EOPF RESUMF 00
USB
Interrupt
Status
E9 UIEN SUSPNDIE RSTE RSTFIE TXD0IE RXD0IE TXD1IE EOPIE RESUMIE 00
USB
Interrupt
Enable
EA UCON0 TSEQ0 STALL0 TX0E RX0E TP0SIZ3 TP0SIZ2 TP0SIZ1 TP0SIZ0 00
USB Endpt0
Xmit Control
EB UCON1 TSEQ1 EP12SEL — FRESUM TP1SIZ3 TP1SIZ2 TP1SIZ1 TP1SIZ0 00
USB Endpt1
Xmit Control
EC UCON2 — — — SOUT EP2E EP1E STALL2 STALL1 00
USB Control
Register
ED USTA RSEQ SETUP IN OUT RP0SIZ3 RP0SIZ2 RP0SIZ1 RP0SIZ0 00
USB Endpt0
Status
EE UADR USBEN UADD6 UADD5 UADD4 UADD3 UADD2 UADD1 UADD0 00
USB
Address
Register
EF UDR0 UDR0.7 UDR0.6 UDR0.5 UDR0.4 UDR0.3 UDR0.2 UDR0.1 UDR0.0 00
USB Endpt0
Data Recv