MULTIJUNCTION TIMERS
10.4 TIO (Input/Output-Related 16-Bit Timer)
10
10.4.14 Operation in TIO Continuous Output Mode (without Correction Function)
(1) Outline of TIO continuous output mode
In continuous output mode, the timer counts down starting from the set value of the counter and when the
counter underflows, it is loaded with the reload 0 register value. Thereafter, this operation is repeated each
time the counter underflows, thus generating consecutive pulses whose waveform is inverted in width of
(reload 0 register set value + 1).
When the timer is enabled (by writing to the enable bit in software or by external input) after setting the
counter and reload 0 register, it starts counting down from the counter’s set value synchronously with the
count clock and when the minimum count is reached, generates an underflow. This underflow causes the
counter to be loaded with the content of the reload 0 register and start counting over again. Thereafter, this
operation is repeated each time an underflow occurs. To stop the counter, disable count by writing to the
enable bit in software.
The F/F output waveform in continuous output mode is inverted (F/F output level changes from low to high or
vice versa) at startup and upon underflow, generating a waveform of consecutive pulses until the timer stops
counting. An interrupt request can be generated each time the counter underflows.
The (counter set value + 1) and (reload 0 register set value + 1) are effective as count values. (For counting
operation, see also Section 10.3.11, “Operation of TOP Continuous Output Mode.”)
(2) Precautions on using TIO continuous output mode
The following describes precautions to be observed when using TIO continuous output mode.
• If the timer is enabled by external input in the same clock period as count is disabled by writing to the
enable bit, the latter has priority so that count is disabled.
• If the counter is accessed for read immediately after being reloaded pursuant to an underflow, the counter
value temporarily reads as H’FFFF but immediately changes to (reload value – 1) at the next clock edge.
• Because the timer operates synchronously with the count clock, a count clock-dependent delay is in-
cluded before F/F output is inverted after the timer is enabled.
32180 Group User’s Manual (Rev.1.0)
10-124
RENESAS [ RENESAS TECHNOLOGY CORP ]
