mc68hc05ct4fn Freescale Semiconductor, Inc, mc68hc05ct4fn Datasheet - Page 81

• Manufacturer Part Number: mc68hc05ct4fn
• Description: Mc68hc05 Family Of Microcontrollers Mcus
• Manufacturer: Freescale Semiconductor, Inc

10.3 Core Timer Control and Status Register
MC68HC05CT4
—
Rev. 2.0
Address
The CTCSR contains the timer interrupt flag, the timer interrupt enable
bits, and the real time interrupt rate select bits.
value of each bit in the CTCSR when coming out of reset.
CTOF — Core Timer Overflow
RTIF — Real Time Interrupt Flag
TOFE — Timer Overflow Enable
RTIE — Real-Time Interrupt Enable
Reset:
Read:
Write:
Figure 10-2. Core Timer Control and Status Register (CTCSR)
CTOF is a read-only status bit set when the 8-bit ripple counter rolls
over from $FF to $00. Clearing CTOF is done by writing a logic 1 to
TOFC. Writing to CTOF has no effect. Reset clears CTOF.
The real-time interrupt circuit consists of a 3-stage divider and a one-
of-four selector. The clock frequency that drives the RTI circuit is
E/2**14 (or E/16,384) with three additional divider stages, giving a
maximum interrupt period of 64 milliseconds at a bus rate of 2.048
MHz. RTIF is a clearable, read-only status bit and is set when the
output of the chosen (one-of-four selection) stage goes active.
Clearing RTIF is done by writing a logic 1 to RTFC. Writing to RTIF
has no effect. Reset clears RTIF.
When this bit is set, a CPU interrupt request is generated when the
CTOF bit is set. Reset clears this bit.
When this bit is set, a CPU interrupt request is generated when the
RTIF bit is set. Reset clears this bit.
Freescale Semiconductor, Inc.
For More Information On This Product,
$0008
CTOF
Bit 7
0
Go to: www.freescale.com
= Unimplemented
RTIF
6
0
Core Timer
TOFE
5
0
RTIE
4
0
Core Timer Control and Status Register
TOFC
3
0
0
General Release Specification
Figure 10-2
RTRC
2
0
0
RT1
1
1
shows the
Core Timer
Bit 0
RT0
1