ATA6616-P3QW Atmel, ATA6616-P3QW Datasheet - Page 150

• Manufacturer Part Number: ATA6616-P3QW
• Description: TXRX MULTICHIP MOD LIN SIP 38QFN
• Manufacturer: Atmel
• Series: AVR® ATA66 LIN-SBCr

Specifications of ATA6616-P3QW

• Core Processor: AVR
• Core Size: 8-Bit
• Speed: 16MHz
• Connectivity: I²C, LIN, SPI, UART/USART, USI
• Peripherals: Brown-out Detect/Reset, POR, PWM, Temp Sensor, WDT
• Number Of I /o: 16
• Program Memory Size: 8KB (8K x 8)
• Program Memory Type: FLASH
• Eeprom Size: 512 x 8
• Ram Size: 512 x 8
• Voltage - Supply (vcc/vdd): 2.7 V ~ 5.5 V
• Data Converters: A/D 11x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 38-VQFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

150
Atmel ATA6616/ATA6617
The Timer/Counter Overflow Flag (TOV1) is set each time the counter reaches TOP. In addi-
tion the OC1A or ICF1 flag is set at the same timer clock cycle as TOV1 is set when either
OCR1A or ICR1 is used for defining the TOP value. If one of the interrupts are enabled, the
interrupt handler routine can be used for updating the TOP and compare values.
When changing the TOP value the program must ensure that the new TOP value is higher or
equal to the value of all of the Compare Registers. If the TOP value is lower than any of the
Compare Registers, a compare match will never occur between the TCNT1 and the
OCR1A/B. Note that when using fixed TOP values the unused bits are masked to zero when
any of the OCR1A/B Registers are written.
The procedure for updating ICR1 differs from updating OCR1A when used for defining the
TOP value. The ICR1 Register is not double buffered. This means that if ICR1 is changed to a
low value when the counter is running with none or a low prescaler value, there is a risk that
the new ICR1 value written is lower than the current value of TCNT1. The result will then be
that the counter will miss the compare match at the TOP value. The counter will then have to
count to the MAX value (0xFFFF) and wrap around starting at 0x0000 before the compare
match can occur. The OCR1A Register however, is double buffered. This feature allows the
OCR1A I/O location to be written anytime. When the OCR1A I/O location is written the value
written will be put into the OCR1A Buffer Register. The OCR1A Compare Register will then be
updated with the value in the Buffer Register at the next timer clock cycle the TCNT1 matches
TOP. The update is done at the same timer clock cycle as the TCNT1 is cleared and the TOV1
flag is set.
Using the ICR1 Register for defining TOP works well when using fixed TOP values. By using
ICR1, the OCR1A Register is free to be used for generating a PWM output on OC1A. How-
ever, if the base PWM frequency is actively changed (by changing the TOP value), using the
OCR1A as TOP is clearly a better choice due to its double buffer feature.
In fast PWM mode, the compare units allow generation of PWM waveforms on the OC1A/B
pins. Setting the COM1x1:0 bits to two will produce a non-inverted PWM and an inverted
PWM output can be generated by setting the COM1A/B1:0 to three (see
158). The actual OC1A/B value will only be visible on the port pin if the data direction for the
port pin is set as output (DDR_OC1A/B) and OC1A/Bi is set. The PWM waveform is generated
by setting (or clearing) the OC1A/B Register at the compare match between OCR1A/B and
TCNT1, and clearing (or setting) the OC1A/B Register at the timer clock cycle the counter is
cleared (changes from TOP to BOTTOM).
The PWM frequency for the output can be calculated by the following equation:
The N variable represents the prescaler divider (1, 8, 64, 256, or 1024).
The extreme values for the OCR1A/B Register represents special cases when generating a
PWM waveform output in the fast PWM mode. If the OCR1A/B is set equal to BOTTOM
(0x0000) the output will be a narrow spike for each TOP+1 timer clock cycle. Setting the
OCR1A/B equal to TOP will result in a constant high or low output (depending on the polarity
of the output set by the COM1A/B1:0 bits.)
f
OCnxPWM
=
------------------------------------- -
N
f
clk_I/O
1
+
TOP
Table 4-36 on page
9132D–AUTO–12/10