Modular Input/Output Subsystem (MIOS14)
MPC561/MPC563 Reference Manual, Rev. 1.2
Freescale Semiconductor
17-47
Figure 17-25. MPWMSM Block Diagram
17.10.1 MPWMSM Terminology
Terminology used in the MIOS14 pulse width modulation submodule includes the following:
Bits of resolution
The MPWMSM contains a 16-bit modulus down-counter that counts from the
desired loaded value to 0x0001. The term “bits of resolution” is used in this
document to indicate the size of the equivalent free running binary counter. To
cover the worst case, the number of bits is rounded to the lower number. For
example, if the counter is preset with a value between 128 and 255, it is said to
have seven bits of resolution. If it is preset with a value between 256 and 511, it is
said to have eight bits of resolution, and so on.
Resolution The
term
“resolution” is used in this document to define the minimum MPWMSM
output increment in time units.
17.10.2 MPWMSM Features
•
Output pulse width modulated (PWM) signal generation with no software intervention
•
Built-in 8-bit programmable prescaler clocked by the MCPSM
16-bit Down Counter
8- bit Prescaler
PS7 - PS0
Output
Submodule bus
Buffer
(Ncount)
= 0x0001
POL
Next Period Register
MPWMPERR
16-bit
Pulse Width Register
Next Pulse Width
Register
MPWMPULR2
Output
Flip-Flop
PIN
TRSP
EN
Counter
Output
Signal
MPWMCNTR
Request Bus
<= Comparator
LOAD
FREN
Clock
FLAG
EN
DDR
Output
Logic
Output
Logic
MPWMPULR1
Summary of Contents for MPC561
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