M16C30L Datasheet, PDF (82/166 Pages) Renesas Technology Corp – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

Timer A
Mitsubishi microcomputers
M16C / 30L 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. Timer A2 can count a single-phase and a two-phase external
signal. Table 1.14.2 lists timer specifications when counting a single-phase external signal. Figure
1.14.8 shows the timer Ai mode register in event counter mode.
Table 1.14.3 lists timer specifications when counting a two-phase external signal. Figure 1.14.9 shows
the timer Ai mode register in event counter mode.
Table 1.14.2. Timer specifications in event counter mode (when not processing two-phase pulse signal)
Item
Count source
Count operation
Specification
• External signals input to TAiIN 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)
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.
Timer Ai mode register
(When not using two-phase pulse signal processing)
b7 b6 b5 b4 b3 b2 b1 b0
0
01
Symbol
Address
When reset
TAiMR(i = 0 to 2) 039616 to 039816
0016
Bit symbol
TMOD0
TMOD1
MR0
MR1
MR2
MR3
TCK0
Bit name
Function
RW
Operation mode select bit ^{b1 b0}
0 1 : Event counter mode (Note 1)
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)
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 (Must always be “0” in event counter mode)
Count operation type
select bit
0 : Reload type
1 : Free-run type
TCK1
Invalid when not using two-phase pulse signal processing
Can be “0” or “1”
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”.
Figure 1.14.8. Timer Ai mode register in event counter mode
81