Mitsubishi microcomputers
M16C / 61 Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Timer A
74
Item
Specification
Count source
Count operation
f
1
, f
8
, f
32
, f
C32
Down count
When the timer underflows, it reloads the reload register contents before continuing counting
1/(n+1)
n : Set value
Count start flag is set (= 1)
Count start flag is reset (= 0)
When the timer underflows
Programmable I/O port or gate input
Programmable I/O port or pulse output
Count value can be read out by reading timer Ai register
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)
Gate function
Counting can be started and stopped by the TAi
IN
pin’s input signal
Pulse output function
Each time the timer underflows, the TAi
OUT
pin’s polarity is reversed
Divide ratio
Count start condition
Count stop condition
Interrupt request generation timing
TAi
IN
pin function
TAi
OUT
pin function
Read from timer
Write to timer
Select function
(1) Timer mode
In this mode, the timer counts an internally generated count source. (See Table 1.16.1.) Figure 1.16.6
shows the timer Ai mode register in timer mode.
Table 1.16.1. Specifications of timer mode
Note 1: The settings of the corresponding port register and port direction register
are invalid.
Note 2: The bit can be “0” or “1”.
Note 3: Set the corresponding port direction register to “0”.
Timer Ai mode register
Symbol
TAiMR(i=0 to 4)
Address
When reset
00
16
0396
16
to 039A
16
Bit name
Function
Bit symbol
W
A
R
b7
b6
b5
0
b4
b3
b2
b1
0 0
b0
Operation mode
select bit
0 0 : Timer mode
b1 b0
TMOD1
MR0
TMOD0
Pulse output function
select bit
0 : Pulse is not output
(TA
iOUT
pin is a normal port pin)
1 : Pulse is output (Note 1)
(TA
iOUT
pin is a pulse output pin)
Gate function select bit
0 X
(Note 2)
: Gate function not available
(TAi
IN
pin is a normal port pin)
1 0 : Timer counts only when TA
iIN
pin is
held “L” (Note 3)
1 1 : Timer counts only when TA
iIN
pin is
held “H” (Note 3)
b4 b3
MR2
MR1
MR3
0 (Must always be fixed to “0” in timer mode)
0 0 : f
1
0 1 : f
8
1 0 : f
32
1 1 : f
C32
b7 b6
TCK1
TCK0
Count source select bit
AA
AA
A
A
AA
AA
AA
A
A
Figure 1.16.6. Timer Ai mode register in timer mode