System Configuration and Protection
MPC561/MPC563 Reference Manual, Rev. 1.2
6-20
Freescale Semiconductor
is not affected by reset and operates in all low-power modes. It is initialized by software. The RTC can be
programmed to generate a maskable interrupt when the time value matches the value programmed in its
associated alarm register. It can also be programmed to generate an interrupt once a second. A control and
status register is used to enable or disable the different functions and to report the interrupt source.
NOTE
PITRTCLK can be divided by 4 or 256. See
for default settings.
Figure 6-7. RTC Block Diagram
6.1.9
Periodic Interrupt Timer (PIT)
The periodic interrupt timer consists of a 16-bit counter clocked by the PITRTCLK clock signal supplied
by the clock module as shown in
The 16-bit counter counts down to zero when loaded with a value from the PITC register. After the timer
reaches zero, the PS bit is set and an interrupt is generated if the PIE bit is a logic one. The software service
routine should read the PS bit and then write a 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 written 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 PISCR[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.
PITRTCLK
FREEZE
Divide
32-bit Register (RTCAL)
Sec
Alarm
=
Clock
Disable
Divide
MUX
4-MHz/20-MHz crystal
Interrupt
Interrupt
By 78125
By 15625
Clock
RTSEC
32-bit Counter (RTC)
Summary of Contents for MPC561
Page 84: ...MPC561 MPC563 Reference Manual Rev 1 2 lxxxiv Freescale Semiconductor...
Page 144: ...Signal Descriptions MPC561 MPC563 Reference Manual Rev 1 2 2 46 Freescale Semiconductor...
Page 206: ...Central Processing Unit MPC561 MPC563 Reference Manual Rev 1 2 3 62 Freescale Semiconductor...
Page 302: ...Reset MPC561 MPC563 Reference Manual Rev 1 2 7 14 Freescale Semiconductor...
Page 854: ...Time Processor Unit 3 MPC561 MPC563 Reference Manual Rev 1 2 19 24 Freescale Semiconductor...
Page 968: ...Development Support MPC561 MPC563 Reference Manual Rev 1 2 23 54 Freescale Semiconductor...
Page 1144: ...Internal Memory Map MPC561 MPC563 Reference Manual Rev 1 2 B 34 Freescale Semiconductor...
Page 1212: ...TPU3 ROM Functions MPC561 MPC563 Reference Manual Rev 1 2 D 60 Freescale Semiconductor...
Page 1216: ...Memory Access Timing MPC561 MPC563 Reference Manual Rev 1 2 E 4 Freescale Semiconductor...
