76
TimerA
Mitsubishi microcomputers
M30218 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
(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 17 lists timer specifications when counting a single-phase external signal. Figure
60 shows the timer Ai mode register in event counter mode.
Table 18 lists timer specifications when counting a two-phase external signal. Figure 61 shows the timer
Ai mode register in event counter mode.
Table 17. Timer specifications in event counter mode (when not processing two-phase pulse signal)
Item
Specification
Count source
External signals input to TAiIN pin (effective edge can be selected by software)
TB2 overflow, TAj overflow
Count operation
Up count or down count can be selected by external signal or software
When the timer overflows or underflows, the reload register's content is reloaded
and the timer starts over again.(Note)
Divide ratio
1/ (FFFF16 - n + 1) for up count
1/ (n + 1) for down count
n : Set value
Count start condition
Count start flag is set (= 1)
Count stop condition
Count start flag is reset (= 0)
Interrupt request generation timing
The timer overflows or underflows
TAiIN pin function
Programmable I/O port or count source input
TAiOUT 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 TAiOUT pin’s polarity is reversed
Note: This does not apply when the free-run function is selected.
Bit nameFunction
Timer Ai mode register
Note 1: In event counter mode, the count source is selected by the event / trigger select bit
(addresses 038216 and 038316).
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 TAiOUT pin, the downcount is activated. When “H”,
the upcount is activated. Set the corresponding port direction register to “0”.
SymbolAddressWhen reset
TAiMR(i = 0, 1)039616, 039716
0016
W
R
b7b6b5b4b3b2b1b0
Operation mode select bit
0 1 : Event counter mode (Note 1)
b1 b0
TMOD0
MR0
Pulse output function
select bit
0 : Pulse is not output
(TAiOUT pin is a normal port pin)
1 : Pulse is output (Note 2)
(TAiOUT 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
01
0
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 : TAiOUT pin's input signal (Note 4)
0 : Reload type
1 : Free-run type
Bit symbol
TCK1
Invalid in event counter mode
Can be “0” or “1”
TMOD1
Figure 60. Timer Ai mode register in event counter mode