MOTOROLA
Chapter 19. Time Processor Unit 3
19-3
TPU Operation
multiple service requests are received simultaneously, a priority-scheduling mechanism
grants service based on channel number and assigned priority.
19.2.4
Microengine
The microengine is composed of a control store and an execution unit. Control-store ROM
holds the microcode for each factory-masked time function. When assigned to a channel by
the scheduler, the execution unit executes microcode for a function assigned to that channel
by the CPU. Microcode can also be executed from the dual-port RAM (DPTRAM) module
instead of the control store. The DPTRAM allows emulation and development of custom
TPU microcode without the generation of a microcode ROM mask. Refer to
Section 19.3.6,19.2.5
Host Interface
The host interface registers allow communication between the CPU and the TPU3, both
before and during execution of a time function. The registers are accessible from the IMB
register bit/field definitions and address mapping.
19.2.6
Parameter RAM
Parameter RAM occupies 256 bytes at the top of the system address map. Channel
parameters are organized as 128 16-bit words. Channels zero through 15 each have eight
RAM,” shows how parameter words are organized in memory.
The CPU specifies function parameters by writing to the appropriate RAM address. The
TPU3 reads the RAM to determine channel operation. The TPU3 can also store information
to be read by the CPU in the parameter RAM. Detailed descriptions of the parameters
required by each time function are beyond the scope of this manual. Refer to the TPU
Reference
Manual
(TPURM/AD),
included
in
the
TPU
Literature
Package
(TPULITPAK/D) for more information.
19.3 TPU Operation
All TPU3 functions are related to one of the two 16-bit time bases. Functions are
synthesized by combining sequences of match events and capture events. Because the
primitives are implemented in hardware, the TPU3 can determine precisely when a match
or capture event occurs, and respond rapidly. An event register for each channel provides
for simultaneous match/capture event occurrences on all channels.
When a match or input capture event requiring service occurs, the affected channel
generates a service request to the scheduler. The scheduler determines the priority of the