R8C/18 Group, R8C/19 Group
Rev.1.30
Apr 14, 2006
Page 103 of 233
REJ09B0222-0130
14.1
Timer X
Timer X is an 8-bit timer with an 8-bit prescaler.
The prescaler and timer each consist of a reload register and counter. The reload register and counter
are allocated at the same address, and can be accessed when accessing registers PREX and TX (refer
to
Tables 14.2 to 14.6 the Specifications of Each Modes
).
Figure 14.1 shows a Block Diagram of Timer X. Figures 14.2 and 14.3 show the registers associated
with Timer X.
Timer X has the following five operating modes:
•
Timer mode:
The timer counts the internal count source.
•
Pulse output mode:
The timer counts the internal count source and outputs pulses
which invert the polarity by underflow of the timer.
•
Event counter mode:
The timer counts external pulses.
•
Pulse width measurement mode:
The timer measures the pulse width of an external pulse.
•
Pulse period measurement mode: The timer measures the pulse period of an external pulse.
Figure 14.1
Block Diagram of Timer X
= 00b
= 01b
= 11b
f2
f8
f1
= 10b
fRING
TXCK1 to TXCK0
TXMOD1 to TXMOD0
= 00b or 01b
= 11b
= 10b
TXS bit
Counter
Reload register
PREX register
Counter
Reload register
TX register
Data bus
Timer X interrupt
INT1 interrupt
Write to TX register
Bits TXMOD1 to TXMOD0 = 01b
TXMOD0 to TXMOD1, R0EDG, TXS, TXOCNT: Bits in TXMR register
TXCK0 to TXCK1: Bits in TCSS register
CNTRSEL: Bit in UCON register
Toggle flip-flop
Q
Q
CLR
CK
R0EDG = 1
R0EDG = 0
Polarity
switching
TXMOD1 to TXMOD0
bits = 01b
TXOCNT bit
INT11/CNTR01
CNTR0
INT10/CNTR00
CNTRSEL = 1
CNTRSEL = 0