MB89190/190A series
Chapter 7 8-/16-bit Timer/Counter
7-3
7.
1 Overview of 8-/16-bit Timer/Counter
The 8-/16-bit timer/counter consists of two 8-bit counters (timer 1, timer 2) that
can be used separately (8-bit mode) or concatenated (16-bit mode).
Timer 1 can select an interval timer that increments in synchronization with three
different internal count clocks, or a counter function that increments using the
clock input to the external pin and can output a square wave of any frequency
using the output. Timer 2 has three different internal count clocks, and can only
function as an interval timer function using one of these clocks.
Timer 1 is
concatenated in the 16-bit mode.
T Interval timer function
The interval timer function generates repeated interrupt requests at any time interval. Also, the interval
timer function can output a square wave of any frequency by reversing the output level of the pin (TO pin)
at each timer interval (timer 1 of the 8-bit mode or 16-bit mode).
In the 8-bit mode, there are two independent timers: timer 1 and timer 2. Each can perform interval
timer operation from the count clock cycle up to 2
8 cycles.
In the 16-bit mode, timer 1 and timer 2 work as the lower and upper of a concatenated 16-bit timer,
respectively, and can perform interval timer operation from the count clock cycle up to 2
16 cycles.
The count clock can be selected from three different internal clocks (the counter function works when
timer 1 selects the external clock).
The timer 1 output cycle can be used as a continuous activation clock for an A/D converter.
Tables 7-1a to 7-1c show the interval time and the square-wave output range in each mode.
Table 7-1a Interval Time and Square Wave Output Range for Timer 1 in 8-bit Mode
Count clock cycle
Interval time
Square wave output range (Hz)
2 tINST
2 tINST to 2
9 tINST
1/ (2
2 tINST) to 1/ (210 tINST)
32 tINST
2
5 tINST to 213 tINST
1/ (2
6 tINST) to 1/ (214 tINST)
Internal count clock
512 tINST
2
9 tINST to 217 tINST
1/ (2
10 tINST) to 1/ (218 tINST)
External clock
1 text
1 text to 2
8 text
1/ (2 text) to 1/ (2
9 text)
Table 7-1b Interval Time and Square Wave Output Range for Timer 2 in 8-bit Mode
Count clock cycle
Interval time
2 tINST
2 tINST to 2
9 t
INST
32 tINST
2
5 tINST to 213 tINST
Internal count clock
512 tINST
2
9 tINST to 217 tINST