ata6616 ATMEL Corporation, ata6616 Datasheet - Page 50

• Manufacturer Part Number: ata6616
• Description: Microcontroller With Lin Transceiver, 5v Regulator And Watchdog
• Manufacturer: ATMEL Corporation

4.5.1.4
4.5.1.5
4.5.2
50
ATA6616/ATA6617 [Preliminary]
Clock Sources
Asynchronous Timer Clock – clk
ADC Clock – clk
The asynchronous timer clock allows the asynchronous Timer/Counter to be clocked directly
from an external clock or an external low frequency crystal. The dedicated clock domain allows
using this Timer/Counter as a real-time counter even when the device is in sleep mode.
The ADC is provided with a dedicated clock domain. This allows halting the CPU and I/O clocks
in order to reduce noise generated by digital circuitry. This gives more accurate ADC conversion
results.
The device has the following clock source options, selectable by Flash Fuse bits (default) or by
the CLKSELR register (dynamic clock switch circuit) as shown below. The clock from the
selected source is input to the AVR clock generator, and routed to the appropriate modules.
Table 4-4.
The various choices for each clocking option are given in the following sections.
When the CPU wakes up from Power-down or Power-save, or when a new clock source is
enabled by the dynamic clock switch circuit, the selected clock source is used to time the
start-up, ensuring stable oscillator operation before instruction execution starts.
When the CPU starts from reset, there is an additional delay allowing the power to reach a sta-
ble level before commencing normal operation. The Watchdog Oscillator is used for timing this
real-time part of the start-up sequence. The number of WDT Oscillator cycles used for each
time-out is shown in
Table 4-5.
Device Clocking Option
External Clock
Calibrated Internal RC Oscillator 8.0 MHz
Watchdog Oscillator 128 kHz
External Low-frequency Oscillator
External Crystal/Ceramic Resonator (0.4 - 0.9 MHz)
External Crystal/Ceramic Resonator (0.9 - 3.0 MHz)
External Crystal/Ceramic Resonator (3.0 - 8.0 MHz)
External Crystal/Ceramic Resonator (8.0 - 16.0 MHz)
Notes:
ADC
Typ. Time-out (Vcc = 5.0V)
1. For all fuses “1” means unprogrammed while “0” means programmed
2. Flash Fuse bits
3. CLKSELR register bits
4.1 ms
65 ms
Device Clocking Options Select
Number of Watchdog Oscillator Cycles
ASY
Table
4-5.
Typ. Time-out (Vcc = 5.0V)
4.3 ms
69 ms
(1)
DRAFT
versus PB4 and PB5 Functionality
CKSEL3..0
CSEL3..0
0000
0010
0011
100x
101x
110x
111x
01xx
b
b
b
b
b
b
b
b
(3)
(2)
XTAL1
XTAL1
XTAL1
XTAL1
XTAL1
Number of Cycles
CLKI
PB4
I/O
I/O
8K (8,192)
512
9132A–AUTO–10/08
CLKO - I/O
CLKO - I/O
CLKO - I/O
XTAL2
XTAL2
XTAL2
XTAL2
XTAL2
PB5