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CHAPTER 5 16-BIT RELOAD TIMER
5.1
Overview of the 16-bit Reload Timer
The 16-bit reload timer consists of a 16-bit down counter, a 16-bit reload register, a
prescaler for creating an internal count clock, and a control register.
■ Overview of the 16-bit Reload Timer
The MB91319 series has three built-in channels, numbered 0 to 2, for the 16-bit reload timer.
Channels 0 and 1 support the activation of DMA transfers resulting from interrupts.
The input clock can be selected from three internal clocks (machine clock divided by 2, 8, and 32)
and an external clock.
The output pin (TOUT) outputs a toggle output waveform whenever an underflow occurs in reload
mode and outputs a square wave that indicates that counting is in progress in one-shot mode.
The input pin (TIN) can be used as the event input in external event count mode and as the
trigger or gate input in internal clock mode.
The external event count function, when used in reload mode, can be used as a divider for
external clock mode.
■ Block Diagram
Figure 5.1-1 is a block diagram of the 16-bit reload timer.
16
8
16
2
3
138
Figure 5.1-1 Block Diagram of the 16-bit Reload Timer
16-bit reload register
16-bit down counter UF
2
GATE
CSL1
Clock selector
CSL0
EXCK
φ
φ
φ
Prescaler clear
1
3
5
2
2
2
Internal clock
Reload
OUT
CTL.
2
Re-trigger
IN CTL.
3
MOD0
MOD1
MOD2
RELD
OUTE
OUTL
INTE
UF
IRQ
CNTE
TRG
Port (TIN)
Port (TOUT)
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