Modular Input/Output Subsystem (MIOS14)
MPC561/MPC563 Reference Manual, Rev. 1.2
17-54
Freescale Semiconductor
The flag bit is a status bit which indicates, when set, that the output period has started and that registers
MPWMPERR and MPWMPULR1 are available for updates when in double-buffered mode. The level of
the resulting interrupt is determined in the MIRSM.
17.10.3.9 MPWMSM Port Functions
The MPWMSM has one dedicated I/O external signal.
The output flip-flop is the basic output of the MPWMSM. Except when the pulse width is at 100% or 0%,
the output flip-flop is reset at the beginning of each period and is set at the beginning of the designated
pulse width until the end of the period. As a software option, the polarity of the signal presented to the
output signal may be the state of the output flip-flop or the inverse of the output flip-flop.
The MPWMSM is connected to an external, input/output signal. When in the disabled mode, the POL bit
(polarity) and the DDR bit (data direction) in the SCR register allow the MPWMSM to be used as an I/O
port.
17.10.3.10 MPWMSM Data Coherency
Byte accesses to MPWMPULR and MPWMPERR are supported, but are not recommended as the transfer
from the primary registers to the secondary registers are done as a 16-bit word transfer.
For most MPWMSM operations, 16-bit accesses are sufficient and long word accesses (32-bit) are treated
as two 16-bit accesses, with one exception — a long word write to the period/pulse width registers. In this
case, if the long word write takes place within the PWM period, there is no visible effect on the output
signal and the new values stored in MPWMPERR and MPWMPULR are ready to be loaded into the buffer
registers at the start of the next period. If, however, the long word write coincides with the end of the
period, then the transfer of values from the primary to the secondary registers is delayed until the end of
the next period; during this period the previous values are used for the period and width. This feature
enables updates of the period and pulse-width values without getting erroneous pulses.
17.10.4 Modular Input/Output Bus (MIOS14) Interface
The MPWMSM is connected to all the signals in the read/write and control bus, to allow data transfer from
and to the MPWMSM registers, and to control the MPWMSM in the different possible situations.
•
The MPWMSM is not using any of the 16-bit counter buses.
•
The MPWMSM uses the request bus to transmit to the request submodule.
17.10.5 Effect of RESET on MPWMSM
The MPWMSM is affected by reset according to what is described in the section related to register
description.
The MPWMPERR, MPWMPULR, and MPWMCNTR registers, together with the clock prescaler register
bits, must be initialized by software, since they are undefined after hardware reset.
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...