MC68HC05L28 Datasheet, PDF (51/156 Pages) Motorola, Inc – Flexible general-purpose microcomputer

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CORE TIMER
The MC68HC05L28 has a 15-stage ripple counter called the core timer (CTIMER). Features of this
timer are: timer overflow, power-on reset (POR), real time interrupt (RTI) with four selectable
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interrupt rates, and a computer operating properly (COP) watchdog timer.
Internal bus
8
Internal processor clock
$09 CTCR
(Core timer counter)
8
f_OP / 2¹⁰
f_OP / 2²
f_OP
(÷ 4)
Overflow
detect
circuit
7-bit counter
f_OP / 2¹⁷
f_OP / 2¹⁴
RTI select circuit
$08 CTCSR
(Core timer control & status)
CTOF RTIF CTOFE RTIE 0
8
0 RT1 RT0
Interrupt circuit
POR
TCBP
COP
Clear
COP watchdog
timer
(÷ 8)
To
To interrupt logic
reset
logic
Figure 5-1 Core timer block diagram
MC68HC05L28
CORE TIMER
TPG
MOTOROLA
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