r8c peripherals 1
TRANSCRIPT
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Course Introduction
Purpose
This course provides an introduction to the peripheral functions built
into R8C Tiny series microcontrollers (MCUs).
Objective Learn about the features and operation of the
TimerRA, TimerRB, TimerRC, TimerRD and TimerRE functions.
Understand the basics of the Watchdog Timer.
Discover how the Power-on Reset (POR) andLow-Voltage Detect (LVD) functions operate.
Content
33 pages
6 questions
Learning Time
35 minutes
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Versatile Set of Timers
Timer RA Timer RB Timer RC Timer RD Timer RETimer structure 8 bit 8-bit 16 bit 2 x 16 bit 4 bit + 8 bit
Prescaler 8 bit 8 bit - - -
Timer Mode Yes Yes Yes Yes -
Pulse Output Mode Yes - - - -
Event Counter Mode Yes - - - -Pulse Width
Measurement ModeYes - - - -
Pulse Period
Measurement ModeYes - - - -
Programmable
Waveform
Generation Mode
- Yes Yes, 2 PWMmodes
Yes, 4 PWMmodes
-
Programmable
One-Shot
Generation Mode
- Yes - - -
Programmable WaitOne-Shot Generation
Mode
- Yes - - -
Input Capture Mode - - Yes Yes -
Output Compare Mode - - Yes Yes Yes
Real Time Clock Mode - - - - Yes
The Watchdog Timeris covered separately in this course.
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PROPERTIES
On passing, 'Finish' button: Goes to Next Slide
On failing, 'Finish' button: Goes to SlideAllow user to leave quiz: At any time
User may view slides after quiz: After passing quiz
User may attempt quiz: Unlimited times
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4
Which of the following timers on the R8C family is 16bit ?Click Done when you are finished.
Timer RA
Timer RBB
Done Reset ShowSolution
A
C Timer RC
Question
Timer RED
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5
Timer RA
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Timer RB
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Timer RC
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Timer RD
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Timer RE
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FFFF
Timer Mode
FF
Reload register Reload register
FF
210
Count Start flag
TRAPRE Pre-scaler TRA Counter
Timer RA
Interruptf2fOCOf8
f1
Count Source
The timer counts an internally generated count source.
Operation: When the timer underflows, it reloads the register contents before continuing to count.
1 0 110 01 2
00h
Timer RA Mode registerTimer RA Mode Register is used to put Timer RA into the
Timer Mode and start/stop the counting.08h
0
1 2
Example: Timer RA
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Pulse Output Mode
1
Reload register Reload register
2
20
Count Start flag
TRAPRE Pre-scaler TRA Counter f2
fOCOf8
f1
Count Source
1
Toggle flip-flop
Q
Q
CK 01
TMOD bits
The timer counts an internally generated count source, the TRAO pin outputs a pulse whose polarity is inverted whenthe timer underflows.
Operation: When the timer underflows, it reloads the register contents before continuing to count.
TRAO
1
Example: Timer RA
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Pulse Output Mode: Timer RA Example
1
Reload Register Reload Register
2
20
Count Start Flag
PREX register TX register f2
fOCOf8
f1
Count Source
1
Toggle flip-flop
Q
Q
CK 01
TMOD bits
The timer counts an internally generated count source, the TRAO pin outputs a pulse whose polarity is inverted when the timer underflows.
Operation: When the timer underflows, it reloads the register contents before continuing to count.
CNTR0
1
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PROPERTIES
On passing, 'Finish' button: Goes to Next Slide
On failing, 'Finish' button: Goes to Next SlideAllow user to leave quiz: After user has completed quiz
User may view slides after quiz: At any time
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Question
Is the following statement true or false?
Click Done when you are finished.
The functionality of the Pulse Output Mode is exactly the same
as in Timer mode, except a pulse is output on the TRAO pin.
True
False
Done
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Generate Complementary Outputs
1
Reload register Reload register
2
20
Count Start flag
TRAPRE Pre-scaler TRA Counter f2
fOCO
f8
f1
Count Source
1
Toggle flip-flop
Q
Q
CK 01
TMOD bits
1
TRAIO
TRAO
TRAIO has the option to be a port pin or an inverted output of TRAO
1
Example: Timer RA
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Event Counter Mode
FF
Reload register Reload register
FF
FFFF0
Count Start Flag
TRAPRE Pre-scaler TRA Counter
External
Count Source
1TRAIO
Timer RA Mode register
00h02h
0
0
2
2
0Ah
102 Timer RAInterrupt
Example: Timer RA
The timer counts an external signal fed to TRAIO pin.
Operation: When the timer underflows, it reloads the register contents before continuing to count.
Timer RA Mode Register is use to put Timer RA into Event
Counter Mode, selects the active edge of the count Source,and starts/stops the counter.
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Pulse Width Measurement Mode
0
Reload register Reload register
5
500
Count Start flag
TRAPRE Pre-scaler TRA Counter
f2
f32
f8
f1
1
TRAIO
Timer RAInterrupt
TRAIO pin
IR bit in TRAICregister
Count Stop Count Stop
The timer measures the pulse width of an external signal fed into the TRAIO pin.
TUNDF bit inTRACR register
Timer Underflow
Count Source
Example: Timer RA
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Pulse Period Measurement Mode: Timer RA
TRAIO pin
Underflow
signal of
prescaler
TRA
contents 0F 0E 0D 0F 0E 0D 0C 0B 0A 09 0F 0E
0F 0E 0D
Timer RA
interrupt
Timer RA active
Edge detected
( TEGDF bit)
0B 0A 09
00 0F
00 0F
Timer RAunderflow
(TUNDF bit)
Contents of readout buffer
Timer RA
reloads
Timer RA
read
Timer RA
read
Cleared to 0 by program
Period being measured
Timer RA
reloads
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Programmable Waveform Gen. Mode
FF
Reload register TRBSC register
FF
1FF0
Count Start flag
TRBPRE Pre-scaler Timer RB Counter f2
TRA UNF
f8
f1
Count Source
1
Toggle flip-flop
Q
Q
CK
01
TMOD bits
FF
TRBPR register
TRBO
P3_1 bit
021010210FF
Primary period Primary periodSecondary period
A signal is output from the TRBO pin which is inverted each time the counter underflows, it reloads the contents of primary reload
register and secondary reload register alternately before continuing to count.
0
0
2 1
102101
Example: Timer RB
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PROPERTIES
On passing, 'Finish' button: Goes to Next Slide
On failing, 'Finish' button: Goes to Next SlideAllow user to leave quiz: After user has completed quiz
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BE
Done ResetShow
Solution
A
C
C
B
A
D
The input that the timer counts is an externalsignal that is fed into the MCU through the
TRAIO pin.
When a trigger occurs, the timer starts
operating once for a given period.
After the Count Start bit has been set, the timerwaits for a high signal on the TRAIO pin.E
D A signal is output from the TRBO pin and isinverted each time the counter underflows.
Question
Event Counter Mode
Pulse Width Measurement Mode
Pulse Period Measurement Mode
Programmable WaveformGenerator Mode
Programmable One-ShotGenerator Mode
Match each timer mode to its function by dragging the letterson the left to their appropriate locations on the right.Click Done when you are finished.
If an underflow occurs while the timer is
counting, the TUNDF bit goes high so that theunderflow can be taken into account.
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Generating a Precise Pulse Width
01 00 01Contents of
TRA
TSTART bit in
TRACR register
Output of TRAO
out pin
Pre-scaler RA
underflow signal
Count Source
IR bit in TRAIC
register
CountStarts
Waveform
Output Starts
Waveform
Output ends
Timer RA
primaryreloads
Set to 1 by program
Set to 0 by program
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Programmable Wait One Shot Generation Mode: Timer RB
In this mode, upon program or external trigger input, the device outputs the one-shot pulse from the TRBO pin after waiting for a given length of time.
When a trigger occurs, the timer starts outputting a pulse for a given length of time equal to the set value in the TRBSC register. This is only after
waiting for the TRBPR register to overflow.
01 00 02
Count Source
Timer RB One
Shot bit
Contents of
TRBPR
Prescaler RB
underflow signal
Interrupt
Request bit in
Timer RB
Interrupt Control
register
TRBO out pin
01 00 01
Set to 1 by program, or set to 1 by
INT0 pin input trigger
Set to 0 when counting
completed
Count
Starts
Timer RB secondary
reloads
Timer RB primary
reloads
Waveform output starts
Waveform output end
Wait starts
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Input Capture Mode
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TimerRC Timer Mode Output Compare
Ti RC PWM M d
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TimerRC PWM Mode
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TimerRD Complementary PWM Mode
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TimerRD Complementary PWM Mode
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PROPERTIES
On passing, 'Finish' button: Goes to Next Slide
On failing, 'Finish' button: Goes to Next SlideAllow user to leave quiz: After user has completed quiz
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Watchdog Timer
1/16
1/128
WatchdogTimer InterruptRequest
WatchdogTimer Reset
PM12 = 0
PM12 = 1
WDC7 = 0
WDC7 = 1
Set to 7FFF16
Write to WDTS register
RESET
CPU
Clock
Pre-scaler
WatchdogTimer
The WDT circuit contains a 15-bit counter that
counts down the clock derived by dividing the CPU
clock by 16 or 128 using the pre-scaler.
P O R t F ti
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Power-On Reset Function
CPUReset IC
CPURes
et ICReset
CCT
No External Reset IC required
0.5
Vdet
5.0
time
time
Internal
state in
Reset
CPU Reset Reset Released
(1/f(RING)) X 32
Vdet = 3.8V 0.5V
More Than 1ms
VCC [V]
S
R
Q
5-bit
counter
Internal
RESET
signal
RESET
fRING-S
VCC > Vdet detectiontrigger
5K
5K
L V lt D t t F ti
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Low Voltage Detect Function
2.7
Vdet
5.0
time
time
Internal
state in
Reset
CPU ResetReset Released
(1/f(RING)) X 32
Vdet = 3.8V 0.5V
VCC [V]
Reset Released
The operation of the LVD function is essentially the
same as the operation of the POR.
LVD O ti
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LVD Operation
Voltage Detect Enable
5.0 V
Vdet
Sampling time
3 to 4 clocks (1/f(RING)) X 32
Internal Reset Signal
Voltage Detect Flag
Voltage Detect
Interrupt Request
Sampling time
3 to 4 clocks
VCC
Interrupt
Acknowledge
Interrupt
Acknowledge
5.0 V
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PROPERTIES
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Which statements describe the LVD function?Select all that apply and then click Done.
Causes the Voltage Detection flag to go to zero when VCC drops below
the detection voltage level
Generates a Voltage Detection Interrupt and an internal Reset signal if
VCC stays below Vdet during the sampling time of 1, 2, 4 or 8 clockcycles
Removes the Reset and generates a Voltage Detection Interrupt request
32 On-chip oscillator cycles after VCC rises above the Vdet level
Resets the microcomputer automatically whenever it is turned on
without using an external Reset circuit
Done
Question
Course Summary
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Timer functions
Timer modes
Watchdog timer
Power-On Reset function
Low Voltage Detect function
Course Summary
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