MPC555CME Freescale Semiconductor, MPC555CME Datasheet - Page 223

• Manufacturer Part Number: MPC555CME
• Description: KIT EVALUATION FOR MPC555
• Manufacturer: Freescale Semiconductor
• Type: Microcontrollerr

Specifications of MPC555CME

• Contents: Module Board, Installation Guide, Power Supply, Cable, Software and more
• Processor To Be Evaluated: MPC555
• Data Bus Width: 32 bit
• Interface Type: RS-232
• For Use With/related Products: MPC555
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

6.9 Periodic Interrupt Timer (PIT)
MPC555
USER’S MANUAL
pitrtclk
The periodic interrupt timer consists of a 16-bit counter clocked by the PITRCLK clock
supplied by the clock module.
The 16-bit counter counts down to zero when loaded with a value from the PITC. After
the timer reaches zero, the PS bit is set and an interrupt is generated if the PIE bit is
is a logic one. The software service routine should read the PS bit and then write it to
zero to terminate the interrupt request. At the next input clock edge, the value in the
PITC is loaded into the counter, and the process starts over again.
When a new value is loaded into the PITC, the periodic timer is updated, the divider is
reset, and the counter begins counting. If the PS bit is not cleared, an interrupt request
is generated. The request remains pending until PS is cleared. If the PS bit is set again
prior to being cleared, the interrupt remains pending until PS is cleared.
Any write to the PITC stops the current countdown, and the count resumes with the
new value in PITC. If the PTE bit is not set, the PIT is unable to count and retains the
old count value. Reads of the PIT have no effect on the counter value.
Clock
/
MPC556
Disable
FREEZE
Clock
SYSTEM CONFIGURATION AND PROTECTION
Figure 6-6 RTC Block Diagram
By 15625
By 78125
RTSEC
Divide
Divide
Rev. 15 October 2000
4-MHz / 20-MHz crystal
MUX
32-bit Register (RTCAL)
32-bit Counter (RTC)
=
MOTOROLA
Interrupt
Interrupt
Alarm
Sec
6-15