SMART ARM-based Microcontrollers
AT03716: Implementation of SAM L Configurable
Custom Logic (CCL) Peripheral
APPLICATION NOTE
Description
The Configurable Custom Logic (CCL) module contains programmable logic
for creating logic gates, sequential logic or a combination of the both. Inputs
can either be I/O pins, internal feedback, peripherals, or events from the
Event System. With CCL, logic operations can be performed without CPU
intervention. This application note presents various features of the CCL,
along with an example application.
The implementation shown in this application note is applicable for the
following devices:
®
•
Atmel | SMART SAM L21
•
Atmel | SMART SAM L22
Atmel-42419B-Implementation-of-SAM-L-Configurable-Custom-Logic-(CCL)-Peripheral_AT03716_Application Note-01/2016
Table of Contents
Description.......................................................................................................................1
1. Module Overview....................................................................................................... 3
1.1.
1.2.
1.3.
1.4.
Truth Table Inputs.........................................................................................................................3
1.1.1.
Masked Input (MASK)....................................................................................................4
1.1.2.
I/O Pin Input (IO)............................................................................................................4
1.1.3.
Linked LUT Input (LINK)................................................................................................ 4
1.1.4.
Internal Feedback Input (FEEDBACK).......................................................................... 4
1.1.5.
Internal Events Input (EVENT)...................................................................................... 4
1.1.6.
Analog Comparator Input (AC)...................................................................................... 5
1.1.7.
Timer/Counter Inputs (TC and ALTTC)..........................................................................5
1.1.8.
Timer/Counter for Control Application Inputs (TCC)...................................................... 5
1.1.9.
Serial Communication Output Transmit Inputs (SERCOM)........................................... 6
Programmable Lookup Table........................................................................................................6
Filter and Edge Detector...............................................................................................................7
Sequential Logic...........................................................................................................................7
2. Example Overview...................................................................................................10
2.1.
2.2.
2.3.
2.4.
Prerequisites...............................................................................................................................11
Peripherals..................................................................................................................................11
Configurations............................................................................................................................ 12
2.3.1.
Configure CCL............................................................................................................. 12
2.3.2.
Configure TC............................................................................................................... 12
2.3.3.
Configure DMAC..........................................................................................................13
2.3.4.
Configure EVSYS........................................................................................................ 13
2.3.5.
Edit Configuration Files................................................................................................13
Main Routine.............................................................................................................................. 13
3. Software License..................................................................................................... 14
4. Revision History.......................................................................................................15
Atmel AT03716: Implementation of SAM L Configurable Custom Logic (CCL) Peripheral
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1.
Module Overview
The Configurable Custom Logic (CCL) module contains programmable logic which can be connected to
I/O pins, internal feedback, peripherals or events. This allows the user to eliminate logic gates on the PCB
for glue logic functions, and introduces additional functionality to applications. CCL can for instance be
used to implement conditional wakeup, where a specific combination of pin and peripheral states enables
the device to wakeup, or optionally to enter a safe state if necessary.
A key element of CCL is the Programmable Lookup Table (LUT). Each LUT consists of three individually
configurable inputs and a truth table, in addition to optional filter, synchronizer and edge detector. Each
LUT can generate an output as a user programmable logic expression from the three inputs. As can be
seen from following block diagram, two LUTs (LUT0 and LUT1, LUT2 and LUT3) are connected to a
sequential logic block, forming a unit. The optional sequential logic can be enabled for complex waveform
generation such as JK flip-flop, RS latch, D latch or gated D flip-flop. The output can be routed to I/O pins,
peripherals, event system or as feedback to the corresponding unit. The output can also be applied as
feedback to a different LUT.
Figure 1-1. Block Diagram
LUT0
LUTCTRL0
(INSEL)
Internal
LUTCTRL0
(FILTSEL)
Events
SEQCTRL
(SEQSEL0)
CTRL
(ENABLE)
Event System
I/O
Truth Table
8
Peripherals
CLK_CCL_APB
GCLK_CCL
LUTCTRL0
(EDGESEL)
Filter / Synch
Edge Detector
CLR
CLR
OUT0
Sequential
Peripherals
I/O
CLR
LUTCTRL0
(ENABLE)
D Q
LUT1
LUTCTRL1
(INSEL)
Internal
LUTCTRL1
(FILTSEL)
Events
CTRL
(ENABLE)
Event System
I/O
Truth Table
Peripherals
CLK_CCL_APB
GCLK_CCL
LUTCTRL1
(EDGESEL)
LUTCTRL1
(ENABLE)
8
Filter / Synch
Edge Detector
CLR
CLR
OUT1
Peripherals
I/O
D Q
UNIT 0
...
.
.
Event System
1.1.
UNIT x
OUT2x-1
Peripherals
I/O
Truth Table Inputs
The inputs IN[x] to the LUT can be selected from the following sources:
•
Masked
•
I/O Pin
•
Linked LUT
•
Internal Feedback
•
Events
•
Peripherals:
– Analog Comparator output (AC)
– Timer/Counters waveform outputs (TC/TCC)
– Serial Communication output transmit interface (SERCOM)
Atmel AT03716: Implementation of SAM L Configurable Custom Logic (CCL) Peripheral
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1.1.1.
Masked Input (MASK)
This is the default option for the inputs. When an input is masked, the value on the corresponding input
will always be zero. If only two inputs are of interest, the unused input should be masked to ensure that its
value is constant. Masked input is selected by writing the Input y Source Selection bit group in the LUT
Control x register (LUTCTRLx.INSELy) to 0x0.
1.1.2.
I/O Pin Input (IO)
I/O pins can be applied as inputs for the LUTs. An overview of available LUT I/O pins can be found in the
"PORT Function Multiplexing" table in the "I/O Multiplexing and Considerations" chapter in the device
datasheet. I/O pin input is selected by writing the Input y Source Selection bit group in the LUT Control x
register (LUTCTRLx.INSELy) to 0x4.
To enable a peripheral function on a pin, the Peripheral Multiplexer Enable bit in the Pin Configuration
register (PINCFGn.PMUXEN) corresponding to specific pin must be written to one. The selection of
peripheral function is done by writing to the Peripheral Multiplexing Odd and Even bits in the Peripheral
Multiplexing register (PMUXn.PMUXE/O). The following code example shows how an I/O pin is
multiplexed as LUT0 input 0 using ASF:
struct system_pinmux_config lut0_out_pin_conf;
system_pinmux_get_config_defaults(&lut0_out_pin_conf);
lut0_out_pin_conf.direction
= SYSTEM_PINMUX_PIN_DIR_OUTPUT;
lut0_out_pin_conf.mux_position = MUX_CCL_OUTPUT;
system_pinmux_pin_set_config(PIN_CCL_OUTPUT, &lut0_out_pin_conf);
Note: Not all LUTs can be connected to pins on the lower pin count devices.
1.1.3.
Linked LUT Input (LINK)
The LUTs can be linked by applying a LUT output as input to a different LUT. Linking LUTs can for
instance be used to create more complex waveforms, or simply to increase the number of available
inputs. When LUTs are connected in cascade the number of inputs is 2N+1 where N is the number of
connected LUTs. Linked LUT input is selected by writing the Input y Source Selection bit group in the LUT
Control x register (LUTCTRLx.INSELy) to 0x2. The following table shows the corresponding inputs and
outputs available for linking.
Table 1-1. LUT Linked Inputs
LUT
IN[x]
Output from LUT
LUT0
x = 0,1,2
LUT1
LUT1
x = 0,1,2
LUT2
LUT2
x = 0,1,2
LUT3
LUT3
x = 0,1,2
LUT0
1.1.4.
Internal Feedback Input (FEEDBACK)
The output from the sequential logic block can be selected as input to the LUTs in the corresponding unit.
Internal feedback input is selected by writing the Input y Source Selection bit group in the LUT Control x
register (LUTCTRLx.INSELy) to 0x1.
1.1.5.
Internal Events Input (EVENT)
Asynchronous events from Event System can be used as input selection. One event input line is available
for each LUT and can be selected on each LUT input. Internal events input is selected by writing the Input
y Source Selection bit group in the LUT Control x register (LUTCTRLx.INSELy) to 0x3. Before enabling
the event selection, the Event System must be configured.
Atmel AT03716: Implementation of SAM L Configurable Custom Logic (CCL) Peripheral
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The CCL includes an edge detector which generates an internal strobe when the event rising edge is
detected. The strobe duration is one GCLK_CCL clock cycle. To ensure the proper operation, the
following steps must be followed:
•
Enable the GCLK_CCL clock
•
Configure Event System to route the desired event asynchronously
•
Set the Inverted Event Input Enable bit in LUT Control register (LUTCTRLx.INVEI = 1) if a strobe
must be generated on the event input falling edge
•
Set the Event Input Enable bit in LUT Control register (LUTCTRLx.LUTEI = 1)
1.1.6.
Analog Comparator Input (AC)
The AC outputs can be used as input source for the LUT. The AC compares voltage levels for two inputs,
and provides a digital output based on this comparison. Each AC instance contains two comparators and
each LUT can be connected to one designated comparator, shown in the following table. Analog
comparator input is selected by writing the Input y Source Selection bit group in the LUT Control x register
(LUTCTRLx.INSELy) to 0x5. Before selecting the comparator output, the AC must be configured.
Table 1-2. LUT AC Inputs
1.1.7.
LUT
IN[x]
AC
CMP
LUT0
x = 0,1,2
AC0
CMP0
LUT1
x = 0,1,2
LUT2
x = 0,1,2
LUT3
x = 0,1,2
CMP1
AC1
CMP0
CMP1
Timer/Counter Inputs (TC and ALTTC)
The TC waveform output WO[0] can be used as input source. A total of two TCs can be applied as inputs
to one LUT, default and alternative TC. TC waveform input is selected by writing the Input y Source
Selection bit group in the LUT Control x register (LUTCTRLx.INSELy) to 0x6 or 0x7. For LUTx, TCx and
the subsequent TC(x+1) instances are available as default and alternative TC selections. The
corresponding LUTs and input TCs are indicated in the following table. Before selecting the TC waveform
output, the TC must be configured.
Table 1-3. LUT TC Inputs
LUT
IN[x]
TC
ALTTC
LUT0
x = 0,1,2
TC0
TC1
LUT1
x = 0,1,2
TC1
TC2
LUT2
x = 0,1,2
TC2
TC3
LUT3
x = 0,1,2
TC3
TC4
Note: The following errata applies to Rev. A devices of SAM L21. The default TC selection is
TC4/TC0/TC1/TC2 instead of TC0/TC1/TC2/TC3, and the alternate TC selection is TC0/TC1/TC2/TC3
instead of TC1/TC2/ TC3/ TC4. Errata reference: 13406.
1.1.8.
Timer/Counter for Control Application Inputs (TCC)
The TCC waveform outputs WO[2:0] can be used as input source. TCC waveform input is selected by
writing the Input y Source Selection bit group in the LUT Control x register (LUTCTRLx.INSELy) to 0x8.
Each LUT input IN[x] corresponds to a specific TCC waveform output WO[x], implying that a total of three
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TCC waveforms can be applied to each LUT. The corresponding LUTs and TCC waveform outputs are
indicated in the following table. Before selecting the TCC waveform output, the TCC must be configured.
Table 1-4. LUT TCC Inputs
LUT
IN[x]
TCC
WO
LUT0
x=0
TCC0
WO[0]
LUT1
LUT2
LUT3
1.1.9.
x=1
WO[1]
x=2
WO[2]
x=0
TCC1
WO[0]
x=1
WO[1]
x=2
WO[2]
x=0
TCC2
WO[0]
x=1
WO[1]
x=2
WO[2]
x=0
TCC3
WO[0]
x=1
WO[1]
x=2
WO[2]
Serial Communication Output Transmit Inputs (SERCOM)
The SERCOM transmitter output can be used as input source. The transmitter output is TxD for USART,
MOSI for SPI, and SDA for I2C. SERCOM input is selected by writing the Input y Source Selection bit
group in the LUT Control x register (LUTCTRLx.INSELy) to 0x9. LUTx can be connected to SERCOMx,
as indicated in the following table. Before selecting the SERCOM as input source, the SERCOM must be
configured.
Table 1-5. LUT SERCOM Inputs
1.2.
LUT
IN[x]
SERCOM
LUT0
x = 0,1,2
SERCOM0
LUT1
x = 0,1,2
SERCOM1
LUT2
x = 0,1,2
SERCOM2
LUT3
x = 0,1,2
SERCOM3
Programmable Lookup Table
Each LUT has a truth table determining its output value based on the input values. All combinations of the
three inputs IN[0], IN[1] and IN[2] are indicated in the below table, where each combination corresponds
to one of the bits in Truth Table bit group in the LUT Control x register (LUTCTRLx.TRUTH). TRUTH must
therefore be set according to the desired output for each combination of inputs. For instance if it is
desired to generate a high output only when all three inputs are low or all three inputs are high, TRUTH[0]
and TRUTH[7] must be written to one (LUTCTRLx.TRUTH written to 0x81). If only the first two inputs are
of interest, and IN[2] is masked, the IN[2] column and the TRUTH[4:7] rows can be neglected since IN[2]
in this case always will be zero.
Atmel AT03716: Implementation of SAM L Configurable Custom Logic (CCL) Peripheral
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Table 1-6. Truth Table of LUT
IN[2]
IN[1]
IN[0]
OUT
0
0
0
TRUTH[0]
0
0
1
TRUTH[1]
0
1
0
TRUTH[2]
0
1
1
TRUTH[3]
1
0
0
TRUTH[4]
1
0
1
TRUTH[5]
1
1
0
TRUTH[6]
1
1
1
TRUTH[7]
Using the above table, one can select specific combinations of inputs, or create standard logic gates.
Examples for creating the most common three input logic gates are shown in the following table.
Table 1-7. Implementation of Logic Gates with Three Inputs
TRUTH[7:0]
1.3.
AND
NAND
OR
NOR
XOR
XNOR
0x80
0x7F
0xFE
0x01
0x16
0xE9
Filter and Edge Detector
By default, the LUT output is a combinatorial function of the LUT inputs. This may cause some short
glitches when the inputs change value. These glitches can be removed by clocking through filters, if
demanded by application needs. The Filter Selection bits in LUT Control register (LUTCTRLx.FILTSEL)
define the synchronizer or digital filter options. When a filter is enabled, the output will be delayed by
three to four GCLK_CCL cycles. One APB clock cycle after a LUT is disabled, all corresponding internal
filter logic is cleared.
The edge detector can be used to generate a pulse when detecting a rising edge on its input. To detect a
falling edge, the truth table should be programmed to provide the opposite levels. The edge detector is
enabled by writing a one to the Edge Selection bit in LUT Control register (LUTCTRLx.EDGESEL). In
order to avoid unpredictable behavior, a valid filter option must be enabled as well. Refer to the Filter
Selection bit group in the LUT Control x register (LUTCTRLx.FILTSEL) for valid filter selections.
1.4.
Sequential Logic
Each LUT pair can be connected to internal sequential logic: D flip flop, JK flip flop, gated D-latch or RSlatch can be selected by writing the corresponding Sequential Selection bits in Sequential Control x
register (SEQCTRLx.SEQSEL). Before using sequential logic, the GCLK clock and optionally each LUT
filter or edge detector, must be enabled.
Gated D Flip-Flop (DFF)
When the DFF is selected, the D-input is driven by the even LUT output (LUT2x), and the G-input is
driven by the odd LUT output (LUT2x+1), as shown in Figure 1-2 D Flip Flop on page 8.
Atmel AT03716: Implementation of SAM L Configurable Custom Logic (CCL) Peripheral
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Figure 1-2. D Flip Flop
When the even LUT is disabled (LUTCTRL2x.ENABLE=0), the flip-flop is asynchronously cleared. The
reset command (R) is kept enabled for one APB clock cycle. In all other cases, the flip-flop output (OUT)
is refreshed on rising edge of the GCLK_CCL, as shown in Table 1-8 DFF Characteristics on page 8.
Table 1-8. DFF Characteristics
R
G
D
OUT
1
X
X
Clear
0
1
1
Set
0
Clear
X
Hold state (no change)
0
JK Flip-Flop (JK)
When this configuration is selected, the J-input is driven by the even LUT output (LUT2x), and the K-input
is driven by the odd LUT output (LUT2x+1), as shown in Figure 1-3 JK Flip Flop on page 8.
Figure 1-3. JK Flip Flop
When the even LUT is disabled (LUTCTRL2x.ENABLE=0), the flip-flop is asynchronously cleared. The
reset command (R) is kept enabled for one APB clock cycle. In all other cases, the flip-flop output (OUT)
is refreshed on rising edge of the GCLK_CCL, as shown in Table 1-9 JK Characteristics on page 8.
Table 1-9. JK Characteristics
R
J
K
OUT
1
X
X
Clear
0
0
0
Hold state (no change)
0
0
1
Clear
0
1
0
Set
0
1
1
Toggle
Gated D-Latch (DLATCH)
When the DLATCH is selected, the D-input is driven by the even LUT output (LUT2x), and the G-input is
driven by the odd LUT output (LUT2x+1), as shown in Figure 1-2 D Flip Flop on page 8.
Atmel AT03716: Implementation of SAM L Configurable Custom Logic (CCL) Peripheral
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Figure 1-4. D-Latch
LUT2x
D
LUT(2x+1)
G
Q
OUT
When the even LUT is disabled (LUTCTRL2x.ENABLE=0), the latch output will be cleared. The G-input is
forced enabled for one more APB clock cycle, and the D-input to zero. In all other cases, the latch output
(OUT) is refreshed as shown in Table 1-10 D-Latch Characteristics on page 9.
Table 1-10. D-Latch Characteristics
G
D
OUT
0
X
Hold state (no change)
1
0
Clear
1
1
Set
RS Latch (RS)
When this configuration is selected, the S-input is driven by the even LUT output (LUT2x), and the Rinput is driven by the odd LUT output (LUT2x+1), as shown in Figure 1-5 RS-Latch on page 9.
Figure 1-5. RS-Latch
RS-latch
LUT2x
S
LUT(2x+1)
R
Q
OUT
When the even LUT is disabled (LUTCTRL2x.ENABLE=0), the latch output will be cleared. The R-input is
forced enabled for one more APB clock cycle and S-input to zero. In all other cases, the latch output
(OUT) is refreshed as shown in Table 1-11 RS-latch Characteristics on page 9.
Table 1-11. RS-latch Characteristics
S
R
OUT
0
0
Hold state (no change)
0
1
Clear
1
0
Set
1
1
Forbidden state
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2.
Example Overview
CCL can be used as a simple logic block for pin logic. A code example with three I/O pin inputs can be
found in the Quick Start Guide for CCL in ASF. In the following application example a more advanced use
case is presented. This example shows how CCL can be used with TCs, together with Event System and
DMAC, to generate an IR encoded signal. The project developed using ASF is available for download as
an attachment, along with this Application Note. Before the example is presented, it is necessary to have
a brief introduction to IR encoding.
IR Encoding
There are many different standards for IR encoding. Most of them involve a fixed carrier frequency which
will be on for a certain period and then off for a certain period. The enabling and disabling of the carrier
frequency is determined by the dutycycle of a waveformed modulation signal. The dutycycle of the
modulation signal will then determine if the transmitting value is a start pulse, a logical one or a logical
zero. E.g. if the carrier frequency is signaled 3/4 of the period, this indicates a logical one, while 1/4
indicates a logical zero. This is illustrated in the following figure.
Figure 2-1. IR Encoded Signal
Start pulse
Logical one
Logical zero
Logical one
In the following example, no specific encoding will be applied but a more general approach where period
and dutycycle can be adjusted is presented.
Implementation
To generate a modulated IR signal, CCL is configured with two TC inputs while the last input is masked.
The default TC is used to generate the carrier frequency of the IR signal while the alternative TC is
applied as the modulation signal. To ensure the modulation signal is synchronized with the carrier
frequency, the alternative TC increments on overflow events generated by the default TC. In the example,
the truth table is written to 0x01. Referring to the Table 1-6 Truth Table of LUT on page 7, this
corresponds to a high output when alternative TC waveform is low and default TC waveform is high. By
adjusting the compare value for the alternative TC, the dutycycle will change, resulting in longer or shorter
intervals of transmitting the carrier frequency.
To update compare value and period, the DMAC will be setup with two channels transferring data from
two arrays in memory to the dedicated TC registers. Using DMAC to update the compare value register
and the peroid register allows the device to operate from Standby sleep mode.
An illustration of the application flow is shown in Figure 2-2 Schematic of Implementation on page 11.
In the following sections, only code for CCL configuration is attached. The configuration of TC, DMAC and
EVSYS will be described but the implementation is only available in the example project enclosed to this
application note.
Atmel AT03716: Implementation of SAM L Configurable Custom Logic (CCL) Peripheral
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Figure 2-2. Schematic of Implementation
GCLK
DMAC
Event System
Default TC
Alternative TC
CCL
2.1.
Prerequisites
Executing the example described in this application note requires:
•
Atmel Studio 7 or later
•
Atmel Software Framework 3.27 or later
•
SAM L21/L22 Xplained Pro Evaluation Kit with USB cable
2.2.
Peripherals
The following peripherals are used in this example:
•
Configurable Custom Logic (CCL)
•
Direct Memory Access Controller (DMAC)
•
Event System (EVSYS)
•
Timer/Counter (TC)
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2.3.
Configurations
2.3.1.
Configure CCL
The CCL must be configured to the desired logical functionality. The configure_ccl_lut0() function
initializes the CCL module with the desired clock generator and configures LUT0 according to the
following settings:
•
Input 0 is default TC
•
Input 1 is alternative TC
•
Input 2 is masked
•
Truth table value set to 0x01
•
Run in Standby enabled
In addition, the encoded signal is multiplexed to the I/O pin corresponding to CCL0 output. The
configuration function follows the ASF standard by creating a configuration struct, loading default settings,
applying necessary changes, and enabling the module.
void configure_ccl_lut0(void)
{
/** Creates a new configuration structure for CCL. */
struct ccl_config conf;
/** Apply the default settings. */
ccl_get_config_defaults(&conf);
conf.clock_source
= GCLK_GENERATOR_1;
conf.run_in_standby = true;
/** Initialize CCL with the user settings. */
ccl_init(&conf);
/** Creates a new configuration structure for LUT0. */
struct ccl_lut_config conf_ccl_lut0;
/** Apply the default settings. */
ccl_lut_get_config_defaults(&conf_ccl_lut0);
/** Configure LUT0. */
conf_ccl_lut0.truth_table_value
conf_ccl_lut0.input0_src_sel
conf_ccl_lut0.input1_src_sel
conf_ccl_lut0.input2_src_sel
=
=
=
=
0x01;
CCL_LUT_INPUT_SRC_TC;
CCL_LUT_INPUT_SRC_ALTTC;
CCL_LUT_INPUT_SRC_MASK;
/** Set up LUT0 output pin. */
struct system_pinmux_config lut0_out_pin_conf;
system_pinmux_get_config_defaults(&lut0_out_pin_conf);
lut0_out_pin_conf.direction
= SYSTEM_PINMUX_PIN_DIR_OUTPUT;
lut0_out_pin_conf.mux_position = CCL_OUTPUT_MUX;
system_pinmux_pin_set_config(CCL_OUTPUT_PIN, &lut0_out_pin_conf);
/** Initialize and enable LUT0 with the user settings. */
ccl_lut_set_config(CCL_LUT_0, &conf_ccl_lut0);
}
2.3.2.
/** Enable CCL module. */
ccl_lut_enable(CCL_LUT_0);
ccl_module_enable();
Configure TC
The two TCs used as inputs for LUT0 are configured in configure_tc_def() and
configure_tc_alt(). The default TC is configured to generate the carrier frequency while the
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alternative TC is used as the modular signal. Both TCs are configured as 8 bit counters with PWM
generation and events enabled. The default TC is configured to generate event on overflow while the
alternative TC is configured to generate event on overflow and to increment counter on incoming event.
For comparison of CCL output signal and the TC waveform outputs, both TCs are multiplexed to I/O pins.
2.3.3.
Configure DMAC
To use DMAC for transferring data it is necessary to configure a DMA resource and transfer descriptor.
The resource contains the peripheral trigger, the trigger action and more channel configurations. The
descriptor contains information regarding the specific data transfer, such as source and destination
address, data size, next descriptor address, transfer counter and more. In the example, two different
channels are used to write to the TC registers. For this purpose, two resources and two descriptors are
needed. The resources are configured with the configure_dma_resource() function while the
descriptors are configured using the configure_dma_channel_x() functions. Both DMA channels are
configured to run in standby with alternative TC overflow as trigger. The next descriptor address field is
used to loop the descriptors back to start, to enable the message to be sent repeatedly. The first channel
is used for updating the alternative TC period. The source address is set to the array containing the
different periods and the destination is the period register. The second channel is used for updating the
alternative TC compare value register. The source address is set to the array containing the different
compare values and the destination is the compare value register.
2.3.4.
Configure EVSYS
Events must be enabled as generators and/or triggers when configuring peripherals. In this example,
event generation on overflow is enabled for both default and alternative TC. The default TC is also set to
count on incomming events and DMAC is set to trigger a transfer on incoming events. In addition, the
event system must be configured to link event generators with event users. In configure_tc_evsys()
the alternative TC is set as event user since this counter should increment incoming events. The event
generator is overflow on the default TC. In configure_dma_evsys()the DMAC is configured to start a
transfer on alternative TC overflow event. DMAC channel 0 and 1 are therefore set as event users while
the event generator is alternative TC overflow. With this setup, the alternative TC period and compare
value registers will be updated after every periodic overflow.
2.3.5.
Edit Configuration Files
The clock system is configured in the included conf_clocks.h header file. To enable Standby sleep
mode operation, the selected clock source is set to run in standby. The peripheral clock source, generic
clock generator 1, is enabled. This clock generator offers a wide range of prescale values. Example
specific defines are placed in the included header file conf_ccl_example.h. The defines enables the
user to switch default and alternative TCs, depending on device revision. This configuration file also
controls the I/O pins and events used in the application.
2.4.
Main Routine
In the main() function, all the previous configuration functions are executed before the TCs are enabled.
To lower the power consumption, the device is set to enter Standby sleep mode. Since peripherals and
clock sources are set to run in standby, the device will continue to generate the encoded signal while
sleeping.
Atmel AT03716: Implementation of SAM L Configurable Custom Logic (CCL) Peripheral
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3.
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Atmel AT03716: Implementation of SAM L Configurable Custom Logic (CCL) Peripheral
[APPLICATION NOTE]
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4.
Revision History
Doc Rev.
Date
Comments
42419B
01/2016
Updated for SAM L22 device
42419A
03/2015
Initial document release
Atmel AT03716: Implementation of SAM L Configurable Custom Logic (CCL) Peripheral
[APPLICATION NOTE]
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