M30201 Datasheet, PDF (53/159 Pages) Mitsubishi Electric Semiconductor – SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER

Timer A
Mitsubishi microcomputers
M30201 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. Timer A0 can count a
single-phase and a two-phase external signal. Table 1.14 lists timer specifications when counting a
single-phase external signal. Figure 1.42 shows the timer A0 mode register in event counter mode.
Table 1.15 lists timer specifications when counting a two-phase external signal. Figure 1.43 shows the
timer A0 mode register in event counter mode.
Table 1.14. Timer specifications in event counter mode (when not processing two-phase pulse signal)
Item
Specification
Count source
• External signals input to TA0IN pin (effective edge can be selected by software)
• TB1 overflow, TX0 overflow, TX2 overflow
Count operation
• 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
TA0IN pin function
Programmable I/O port or count source input
TA0OUT 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 A0 register
Write to timer
• When counting stopped
When a value is written to timer A0 register, it is written to both reload register and counter
• When counting in progress
When a value is written to timer A0 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 TA0OUT pin’s polarity is reversed
Note: This does not apply when the free-run function is selected.
Timer A0 mode register (When not using two-phase pulse signal processing)
b7 b6 b5 b4 b3 b2 b1 b0
0
01
Symbol
TA0MR
Address
039616
When reset
0016
Bit symbol
TMOD0
TMOD1
MR0
MR1
Bit name
Function
RR WW
Operation mode select bit ^{b1 b0}
0 1 : Event counter mode
Pulse output function
select bit
Count polarity
select bit (Note 2)
0 : Pulse is not output
(TA0OUT pin is a normal port pin)
1 : Pulse is output (Note 1)
(TA0OUT pin is a pulse output pin)
0 : Counts external signal's falling edge
1 : Counts external signal's rising edge
MR2
MR3
TCK0
TCK1
Up/down switching
cause select bit
0 : Up/down flag's content
1 : TAiOUT pin's input signal (Note 3)
0 (Must always be fixed to “0” in event counter mode)
Count operation type
select bit
0 : Reload type
1 : Free-run type
Two-phase pulse operation 0 : Normal processing operation
select bit (Note 4)
1 : Multiply-by-4 processing operation
Note 1: Set the corresponding port direction register to “1” (output mode).
Note 2: This bit is valid when only counting an external signal.
Note 3: Set the corresponding port direction register to “0” (input mode).
Note 4: When performing two-phase pulse signal processing, make sure the two-phase
pulse signal processing operation select bit (address 038416) is set to “1” and
event/trigger select bits (addresses 038316) to “00”.
Figure 1.42. Timer A0 mode register in event counter mode
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