AT91SAM7S256C-MU Atmel, AT91SAM7S256C-MU Datasheet - Page 484

• Manufacturer Part Number: AT91SAM7S256C-MU
• Description: IC ARM7 MCU 32BIT 256K 64-QFN
• Manufacturer: Atmel
• Series: AT91SAMr

Specifications of AT91SAM7S256C-MU

• Core Processor: ARM7
• Core Size: 16/32-Bit
• Speed: 55MHz
• Connectivity: I²C, SPI, SSC, UART/USART, USB
• Peripherals: Brown-out Detect/Reset, DMA, POR, PWM, WDT
• Number Of I /o: 32
• Program Memory Size: 256KB (256K x 8)
• Program Memory Type: FLASH
• Ram Size: 64K x 8
• Voltage - Supply (vcc/vdd): 1.65 V ~ 1.95 V
• Data Converters: A/D 8x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 64-VQFN Exposed Pad, 64-HVQFN, 64-SQFN, 64-DHVQFN
• Processor Series: AT91
• Core: ARM7TDMI
• Data Bus Width: 32 bit
• Data Ram Size: 64 KB
• Interface Type: SPI, TWI, USART, USB
• Maximum Clock Frequency: 55 MHz
• Number Of Programmable I/os: 32
• Number Of Timers: 5
• Operating Supply Voltage: 3.3 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Operating Temperature Range: - 40 C to + 85 C
• For Use With: AT91SAM-ICE - EMULATOR FOR AT91 ARM7/ARM9AT91SAM7S-EK - KIT EVAL FOR ARM AT91SAM7S
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Lead Free Status / Rohs Status: Details
• Other names: AT91SAM7S256-MU; AT91SAM7S256-MU

34.5.3
34.5.3.1
34.5.3.2
34.5.3.3
484
AT91SAM7S Series Preliminary
PWM Controller Operations
Initialization
Source Clock Selection Criteria
Changing the Duty Cycle or the Period
Before enabling the output channel, this channel must have been configured by the software
application:
It is possible to synchronize different channels by enabling them at the same time by means of
writing simultaneously several CHIDx bits in the PWM_ENA register.
The large number of source clocks can make selection difficult. The relationship between the
value in the Period Register (PWM_CPRDx) and the Duty Cycle Register (PWM_CDTYx) can
help the user in choosing. The event number written in the Period Register gives the PWM accu-
racy. The Duty Cycle quantum cannot be lower than 1/PWM_CPRDx value. The higher the value
of PWM_CPRDx, the greater the PWM accuracy.
For example, if the user sets 15 (in decimal) in PWM_CPRDx, the user is able to set a value
between 1 up to 14 in PWM_CDTYx Register. The resulting duty cycle quantum cannot be lower
than 1/15 of the PWM period.
It is possible to modulate the output waveform duty cycle or period.
To prevent unexpected output waveform, the user must use the update register (PWM_CUPDx)
to change waveform parameters while the channel is still enabled. The user can write a new
period value or duty cycle value in the update register (PWM_CUPDx). This register holds the
new value until the end of the current cycle and updates the value for the next cycle. Depending
on the CPD field in the PWM_CMRx register, PWM_CUPDx either updates PWM_CPRDx or
PWM_CDTYx. Note that even if the update register is used, the period must not be smaller than
the duty cycle.
• Configuration of the clock generator if DIVA and DIVB are required
• Selection of the clock for each channel (CPRE field in the PWM_CMRx register)
• Configuration of the waveform alignment for each channel (CALG field in the PWM_CMRx
• Configuration of the period for each channel (CPRD in the PWM_CPRDx register). Writing in
• Configuration of the duty cycle for each channel (CDTY in the PWM_CDTYx register).
• Configuration of the output waveform polarity for each channel (CPOL in the PWM_CMRx
• Enable Interrupts (Writing CHIDx in the PWM_IER register)
• Enable the PWM channel (Writing CHIDx in the PWM_ENA register)
• In such a situation, all channels may have the same clock selector configuration and the
register)
PWM_CPRDx Register is possible while the channel is disabled. After validation of the
channel, the user must use PWM_CUPDx Register to update PWM_CPRDx as explained
below.
Writing in PWM_CDTYx Register is possible while the channel is disabled. After validation of
the channel, the user must use PWM_CUPDx Register to update PWM_CDTYx as explained
below.
register)
same period specified.
6175K–ATARM–30-Aug-10