deveopmen
Usage precaution
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
202
Timer B (timer mode, event counter mode)
(1) Reading the timer Bi register while a count is in progress allows reading , with arbitrary timing, the
value of the counter. Reading the timer Bi register with the reload timing gets “FFFF
16
”. Reading the
timer Bi register after setting a value in the timer Bi register with a count halted but before the counter
starts counting gets a proper value.
Timer B (pulse period/pulse width measurement mode)
(1) If changing the measurement mode select bit is set after a count is started, the timer Bi interrupt
request bit goes to “1”.
(2) When the first effective edge is input after a count is started, an indeterminate value is transferred to
the reload register. At this time, timer Bi interrupt request is not generated.
A-D Converter
(1) Write to each bit (except bit 6) of A-D control register 0, to each bit of A-D control register 1, and to bit
0 of A-D control register 2 when A-D conversion is stopped (before a trigger occurs).
In particular, when the Vref connection bit is changed from “0” to “1”, start A-D conversion after an
elapse of 1
μ
s or longer.
(2) When changing A-D operation mode, select analog input pin again.
(3) Using one-shot mode or single sweep mode
Read the correspondence A-D register after confirming A-D conversion is finished. (It is known by A-
D conversion interrupt request bit.)
(4) Using repeat mode, repeat sweep mode 0 or repeat sweep mode 1
Use the undivided main clock as the internal CPU clock.
(5) When f(X
IN
) is faster than 10 MHz, make the frequency 10 MHz or less by dividing.
(6) To carry out A-D conversion properly, charging the internal capacitor C shown in Figure 2.7.29 has to
be completed within a specified period of time. With T as the specified time, time T is the time that
switches SW2 and SW3 are connected to O in Figure 2.7.28. Let output impedance of sensor equiva-
lent circuit be R0, microcomputer’s internal resistance be R, precision (error) of the A-D converter be
X, and the A-D converter’s resolution be Y (Y is 1024 in the 10-bit mode, and 256 in the 8-bit mode).
t
–
Vc is generally V
C
= V
IN
{1 – e
}
And when t = T,
V
C
=V
IN
– X
IN
=V
IN
(1 – Y
Y
e
–
C ( =ln
T
Hence, R0 = –
– R
T
C (R0 + R)
T
–
C (R0 + R)
X
Y
X
Y
X
C ln
Y
X