Mitsubishi microcomputers
M16C / 61 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Timer A
75
Item
Specification
Count source
External signals input to TAi
IN
pin (effective edge can be selected by software)
TB2 overflow, TAj overflow
Up count or down count can be selected by external signal or software
When the timer overflows or underflows, it reloads the reload register con
tents before continuing counting (Note)
1/ (FFFF
16
- n + 1) for up count
1/ (n + 1) for down count
n : Set value
Count start flag is set (= 1)
Count start flag is reset (= 0)
Interrupt request generation timing
The timer overflows or underflows
TAi
IN
pin function
Programmable I/O port or count source input
TAi
OUT
pin function
Programmable I/O port, pulse output, or up/down count select input
Read from timer
Count value can be read out by reading timer Ai register
Write to timer
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)
Select function
Free-run count function
Even when the timer overflows or underflows, the reload register content is not reloaded to it
Pulse output function
Each time the timer overflows or underflows, the TAi
OUT
pin’s polarity is reversed
Note: This does not apply when the free-run function is selected.
Count operation
Divide ratio
Count start condition
Count stop condition
(2) Event counter mode
In this mode, the timer counts an external signal or an internal timer’s overflow. Timers A0 and A1 can
count a single-phase external signal. Timers A2, A3, and A4 can count a single-phase and a two-phase
external signal. Table 1.16.2 lists timer specifications when counting a single-phase external signal.
Figure 1.16.7 shows the timer Ai mode register in event counter mode.
Table 1.16.3 lists timer specifications when counting a two-phase external signal. Figure 1.16.8 shows
the timer Ai mode register in event counter mode.
Table 1.16.2.
Timer specifications in event counter mode (when not processing two-phase pulse signal)
Figure 1.16.7. Timer Ai mode register in event counter mode
Timer Ai mode register
Note 1: In event counter mode, the count source is selected by the event / trigger select bit
(addresses 0382
and 0383
).
Note 2: The settings of the corresponding port register and port direction register are invalid.
Note 3: Valid only when counting an external signal.
Note 4: When an “L” signal is input to the TAi
OUT
pin, the downcount is activated. When “H”,
the upcount is activated. Set the corresponding port direction register to “0”.
Symbol
TAiMR(i = 0, 1)
Address
0396
16
, 0397
16
When reset
00
16
AA
AA
AA
b7
b6
b5
0
b4
b3
b2
b1
0 1
b0
Operation mode select bit
0 1 : Event counter mode
(Note 1)
b1 b0
TMOD0
TMOD1
MR0
Pulse output function
select bit
0 : Pulse is not output
(TA
iOUT
pin is a normal port pin)
1 : Pulse is output (Note 2)
(TA
iOUT
pin is a pulse output pin)
Count polarity
select bit (Note 3)
MR2
MR1
MR3
0 (Must always be fixed to “0” in event counter mode)
TCK0
Count operation type
select bit
0 : Counts external signal's falling edge
1 : Counts external signal's rising edge
Up/down switching
cause select bit
0 : Up/down flag's content
1 : TA
iOUT
pin's input signal (Note 4)
0 : Reload type
1 : Free-run type
Bit symbol
Bit name
Function
TCK1
Invalid in event counter mode
Can be “0” or “1”
AA
AA
AA
AA
AA