Renesas M16C User Manual

Rev.1.10    Jul 01, 2005    page 99 of 318
REJ09B0124-0110

M16C/6N Group (M16C/6NK, M16C/6NM)

12. Timers

This document is under development and its contents are subject to change.

Item

Specification

Count Source

• External signals input to TAiIN pin (effective edge can be selected in program)

• Timer B2 overflows or underflows,

Timer Aj overflows or underflows,

Timer Ak overflows or underflows

Count Operation

• Up-count or down-count can be selected by external signal or program

• When the timer overflows or underflows, it reloads the reload register

contents and continues counting. When operating in free-running mode,

the timer continues counting without reloading.

Divided Ratio

1/ (FFFFh - n + 1) for up-count

1/ (n + 1) for down-count      n : set value of the TAi register    0000h to FFFFh

Count Start Condition

Set the TAiS bit in the TABSR register to “1” (start counting)

Count Stop Condition

Set the TAiS bit to “0” (stop counting)

Interrupt Request Generation Timing Timer overflow or underflow

TAiIN Pin Function

I/O port or count source input

TAiOUT Pin Function

I/O port, pulse output, or up/down-count select input

Read from Timer

Count value can be read by reading the TAi register

Write to Timer

• When not counting and until the 1st count source is input after counting start

Value written to the TAi register is written to both reload register and counter

• When counting (after 1st count source input)

Value written to the TAi register is written to only reload register

(Transferred to counter when reloaded next)

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

Whenever the timer underflows or underflows, the output polarity of

TAiOUT pin is inverted.

When TAiS bit is set to “0” (stop counting), the pin outputs a low.

In event counter mode, the timer counts pulses from an external device or overflows and underflows of

other timers. Timers A2, A3 and A4 can count two-phase external signals. Table 12.2 lists specifications

in event counter mode (when not processing two-phase pulse signal). Figure 12.8 shows TAiMR register

in event counter mode (when not processing two-phase pulse signal). Table 12.3 lists specifications in

event counter mode (when processing two-phase pulse signal with the timers A2, A3 and A4). Figure

12.9 shows TA2MR to TA4MR registers in event counter mode (when processing two-phase pulse signal

with the timers A2, A3 and A4).

i = 0 to 4

j = i - 1, except j = 4 if i = 0

k = i + 1, except k = 0 if i = 4