deveopmen
Timer A
Preliminary Specifications REV.D
Specifications in this manual are tentative and subject to change.
Mitsubishi microcomputers
M16C/80 (100-pin version) group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
90
Timer A
Figure 1.13.1 shows the block diagram of timer A. Figures 1.13.2 to 1.13.4 show the timer A-related registers.
Except in event counter mode, timers A0 through A4 all have the same function. Use the timer Ai mode
register (i = 0 to 4) bits 0 and 1 to choose the desired mode.
Timer A has the four operation modes listed as follows:
Timer mode: The timer counts an internal count source.
Event counter mode: The timer counts pulses from an external source or a timer over flow.
One-shot timer mode: The timer stops counting when the count reaches “0000
16
”.
Pulse width modulation (PWM) mode: The timer outputs pulses of a given width.
Figure 1.13.2. Timer A-related registers (1)
Count start flag
(Address 0340
16
)
Up count/down count
TAi
Addresses
0347
16
0349
16
034B
16
034D
16
TAj
TAk
Timer A0
Timer A1
Timer A2
Timer A3
Timer A4 034F
16
0346
16
0348
16
034A
16
034C
16
034E
16
Timer A4
Timer A0
Timer A1
Timer A2
Timer A3
Timer A1
Timer A2
Timer A3
Timer A4
Timer A0
Always down count except
in event counter mode
Reload register (16)
Counter (16)
Low-order
8 bits
AAAAA
AAAAA
High-order
Clock source
selection
Timer
(gate function)
Timer
One shot
PWM
f
1
f
8
f
32
f
C32
External
trigger
TAi
IN
(i = 0 to 4)
TB2 overflow
Event counter
Clock selection
TAj overflow
(j = i – 1. Note, however, that j = 4 when i = 0)
Pulse output
Toggle flip-flop
TAi
OUT
(i = 0 to 4)
Data bus low-order bits
Data bus high-order bits
AA
Up/down flag
(Address 0344
16
)
Down count
TAk overflow
(k = i + 1. Note, however, that k = 0 when i = 4)
Polarity
selection
Timer Ai mode register
Symbol
TAiMR(i=0 to 4)
Address
When reset
0356
16
to 035A
16
00000X00
2
Bit name
Function
Bit symbol
TMOD0
W
R
b7
b6
b5
b4
b3
b2
b1
b0
0 0 : Timer mode
0 1 : Event counter mode
1 0 : One-shot timer mode
1 1 : Pulse width modulation
(PWM) mode
b1 b0
TCK1
MR3
MR2
MR1
TMOD1
MR0
TCK0
Function varies with each operation mode
Count source select bit
(Function varies with each operation mode)
Operation mode select bit
AA
A
A
AA
A
AA
A
A
AA
AA
A
A
A
This bit is invalid in M16C/80 series.
Port output control is set by the function select registers A and B.
Figure 1.13.1. Block diagram of timer A