
HT48E30
Rev. 0.00
14
January 12, 2004
Preliminary
Label (TMRC)
Bits
Function
PSC0~PSC2
0~2
Defines the prescaler stages, PSC2, PSC1, PSC0=
000: fINT=fSYS/2
001: fINT=fSYS/4
010: fINT=fSYS/8
011: fINT=fSYS/16
100: fINT=fSYS/32
101: fINT=fSYS/64
110: fINT=fSYS/128
111: fINT=fSYS/256
TE
3
Defines the TMR active edge of the timer/event counter 0
(0=active on low to high; 1=active on high to low)
TON
4
Enable or disable timer 0 counting
(0=disabled; 1=enabled)
5
Unused bit, read as
0
TM0
TM1
6
7
Defines the operating mode
01=Event count mode (external clock)
10=Timer mode (internal clock)
11=Pulse width measurement mode
00=Unused
TMRC Register
T M 1
T M 0
T M R
T E
T M 1
T M 0
T O N
P u l s e W i d t h
M e a s u r e m e n t
M o d e C o n t r o l
T i m e r / E v e n t C o u n t e r
P r e l o a d R e g i s t e r
T i m e r / E v e n t
C o u n t e r
D a t a B u s
R e l o a d
O v e r f l o w
t o I n t e r r u p t
1 / 2
B Z
8 - s t a g e P r e s c a l e r
8 - 1 M U X
f S Y S
f I N T
P S C 2 ~ P S C 0
( 1 / 2 ~ 1 / 2 5 6 )
Timer/Event Counter
measurement can be done. Until setting the TON, the
cycle measurement will function again as long as it re-
ceives further transient pulse. Note that, in this operat-
ing mode, the timer/event counter starts counting not
according to the logic level but according to the transient
edges. In the case of counter overflows, the counter is
reloaded from the timer/event counter preload register
and issues the interrupt request just like the other two
modes. To enable the counting operation, the timer ON
bit (TON; bit 4 of TMRC) should be set to 1. In the pulse
width measurement mode, the TON will be cleared au-
tomatically after the measurement cycle is completed.
But in the other two modes the TON can only be reset by
instructions. The overflow of the timer/event counter is
one of the wake-up sources. No matter what the opera-
tion mode is, writing a
0 to ETI can disable the corre-
sponding interrupt services.
In the case of timer/event counter OFF condition, writing
data to the timer/event counter preload register will also
reload that data to the timer/event counter. But if the
timer/event counter is turned on, data written to it will
only be kept in the timer/event counter preload register.
The timer/event counter will still operate until overflow
occurs. When the timer/event counter (reading TMR) is
read, the clock will be blocked to avoid errors. As clock
blocking may results in a counting error, this must be
taken into consideration by the programmer.
The bit0~bit2 of the TMRC can be used to define the
pre-scaling stages of the internal clock sources of
timer/event counter. The definitions are as shown. The
overflow signal of the timer/event counter can be used
to generate PFD signals for buzzer driving.