Mitsubishi microcomputers
M16C / 61 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Timer A
(3) One-shot timer mode
In this mode, the timer operates only once. (See Table 1.16.4.) When a trigger occurs, the timer starts up
and continues operating for a given period. Figure 1.16.9 shows the timer Ai mode register in one-shot
timer mode.
Table 1.16.4. Timer specifications in one-shot timer mode
Item
Count source
Count operation
Specification
f1, f8, f32, fC32
• The timer counts down
• When the count reaches 000016, the timer stops counting after reloading a new count
• If a trigger occurs when counting, the timer reloads a new count and restarts counting
Divide ratio
1/n
n : Set value
Count start condition
• An external trigger is input
• The timer overflows
• The one-shot start flag is set (= 1)
• A new count is reloaded after the count has reached 000016
• The count start flag is reset (= 0)
Count stop condition
Interrupt request generation timing The count reaches 000016
TAiIN pin function
TAiOUT pin function
Read from timer
Write to timer
Programmable I/O port or trigger input
Programmable I/O port or pulse output
When timer Ai register is read, it indicates an indeterminate value
• When counting stopped
When a value is written to timer Ai register, it is written to both reload
register and counter
• When counting in progress
When a value is written to timer Ai register, it is written to only reload register
(Transferred to counter at next reload time)
Timer Ai mode register
b7 b6 b5 b4 b3 b2 b1 b0
Symbol
Address
When reset
0016
TAiMR(i = 0 to 4) 039616 to 039A16
0
1 0
Bit symbol
Bit name
R W
Function
b1 b0
TMOD0
TMOD1
MR0
Operation mode select bit
1 0 : One-shot timer mode
Pulse output function
select bit
0 : Pulse is not output
(TAiOUT pin is a normal port pin)
1 : Pulse is output (Note 1)
(TAiOUT pin is a pulse output pin)
MR1
MR2
0 : Falling edge of TAiIN pin's input signal (Note 3)
1 : Rising edge of TAiIN pin's input signal (Note 3)
External trigger select
bit (Note 2)
0 : One-shot start flag is valid
1 : Selected by event/trigger select
register
Trigger select bit
MR3
0 (Must always be “0” in one-shot timer mode)
b7 b6
TCK0
Count source select bit
0 0 : f
1
8
0 1 : f
TCK1
1 0 : f32
1 1 : fC32
Note 1: The settings of the corresponding port register and port direction register are invalid.
Note 2: Valid only when the TAiIN pin is selected by the event/trigger select bit
(addresses 038216 and 038316). If timer overflow is selected, this bit can be “1” or “0”.
Note 3: Set the corresponding port direction register to “0”.
Figure 1.16.9. Timer Ai mode register in one-shot timer mode
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MITSUBISHI [ Mitsubishi Group ]
