R8C/1A Group, R8C/1B Group
14. Timers
Rev.1.30
Dec 08, 2006
Page 133 of 315
REJ09B0252-0130
14.2.3
Programmable One-shot Generation Mode
In programmable one-shot generation mode, one-shot pulse is output from the TZOUT pin by a program or an
external trigger input (input to the INT0 pin) (refer to
Table 14.9 Programmable One-Shot Generation Mode
Specifications
). When a trigger is generated, the timer starts operating from the point only once for a given
period equal to the set value in the TZPR register. The TZSC register is not used in this mode. Figure 14.19
shows Registers TZMR and PUM in Programmable One-Shot Generation Mode. Figure 14.20 shows an
Operating Example in Programmable One-Shot Generation Mode.
NOTES:
1. Set the TZS bit in the TZMR register to 1 (count starts).
2. Set the TZS bit to 1 (count starts), the INT0EN bit in the INTEN register to 1 (enables INT0 input),
and the INOSTG bit in the PUM register to 1 (INT0 one-shot trigger enabled). A trigger which is input
during the count cannot be acknowledged, however an INT0 interrupt request is generated.
3. The set value is reflected at the following one-shot pulse after writing to the TZPR register.
Table 14.9
Programmable One-Shot Generation Mode Specifications
Item
Specification
Count sources
f1, f2, f8, Timer X underflow
Count operations
• Decrement the value set in the TZPR register
• When the timer underflows, it reloads the contents of the reload register before
the count completes and the TZOS bit is set to 0 (one-shot stops).
• When the count stops, the timer reloads the contents of the reload register
before it stops.
One-shot pulse
output time
(n+1)(m+1)/fi
fi: Count source frequency,
n: value set in PREZ register, m: value set in TZPR register
Count start conditions • Set the TZOS bit in the TZOC register to 1 (one-shot starts).
(1)
• Input active trigger to the INT0 pin
(2)
Count stop conditions • When reloading completes after the count value is set to 00h.
• When the TZS bit in the TZMR register is set to 0 (count stops).
• When the TZOS bit in the TZOC register is set to 0 (one-shot stops).
Interrupt request
generation timing
In half a cycle of the count source, after the timer underflows (at the same time as
the TZOUT output ends) [timer Z interrupt].
TZOUT pin function
Pulse output
(To use this pin as a programmable I/O port, select timer mode.)
INT0 pin function
• When the INOSTG bit in the PUM register is set to 0 (INT0 one-shot trigger
disabled): programmable I/O port or INT0 interrupt input
• When the INOSTG bit in the PUM register is set to 1 (INT0 one-shot trigger
enabled): external trigger (INT0 interrupt input)
Read from timer
The count value can be read out by reading registers TZPR and PREZ.
Write to timer
The value written to registers TZPR and PREZ is written to the reload register
only
(3)
.
Select functions
• Output level latch select function
The TZOPL bit can select the output level of the one-shot pulse waveform.
• INT0 pin one-shot trigger control and polarity select functions
The INOSTG bit can select the trigger as active or inactive from the INT0 pin.
Also, the INOSEG bit can select the active trigger polarity.
