at43usb320a ATMEL Corporation, at43usb320a Datasheet - Page 39

• Manufacturer Part Number: at43usb320a
• Description: Full-speed Usb Microcontroller With An Embedded Hub
• Manufacturer: ATMEL Corporation

8-bit
Timer/Counter0
Figure 10. Timer/Counter0 Block Diagram
1443E–USB–4/04
7
Timer Int. Mask Register
Timer/Counter0
(TCNT0)
The 8-bit Timer/Counter0 can select clock source from CK, prescaled CK or an external pin. In
addition it can be stopped as described in the specification for the Timer/Counter0 Control
Register (TCCR0). The overflow status flag is found in the Timer/Counter Interrupt Flag Regis-
ter (TIFR). Control signals are found in the Timer/Counter0 Control Register (TCCR0). The
interrupt enable/disable settings for Timer/Counter0 are found in the Timer/Counter Interrupt
Mask Register - TIMSK.
When Timer/Counter0 is externally clocked, the external signal is synchronized with the oscil-
lator frequency of the CPU. To assure proper sampling of the external clock, the minimum
time between two external clock transitions must be at least one internal CPU clock period.
The external clock signal is sampled on the rising edge of the internal CPU clock.
The 8-bit Timer/Counter0 features both a high resolution and a high accuracy usage with the
lower prescaling opportunities. Similarly, the high prescaling opportunities make the
Timer/Counter0 useful for lower speed functions or exact timing functions with infrequent
actions.
(TIMSK)
0
Overflow IRQ
T/C0
T/C Clock Source
Timer Int. Flag Register
(TIFR)
Control
Logic
T/C0 Control Register
AT43USB320A
(TCCR0)
CK
T0
39