Motorola DSP56301 - Manual (Page 25)

DSP56300 Core Functional Blocks
Overview 1 -9
1.4.4 PLL and Clock Oscillator
The clock generator in the DSP56300 core comprises two main blocks: the PLL, which
performs clock input division, frequency multiplication, and skew elimination; and the clock
generator, which performs low-power division and clock pulse generation. These features
allow you to:
n Change the low-power divide factor without losing the lock
n Output a clock with skew elimination
The PLL allows the processor to operate at a high internal clock frequency using a
low-frequency clock input, a feature that offers two immediate benefits:
n A lower-frequency clock input reduces the overall electromagnetic interference
generated by a system.
n The ability to oscillate at different frequencies reduces costs by eliminating the need to
add additional oscillators to a system.
1.4.5 JTAG TAP and OnCE Module
In the DSP56300 core is a dedicated user-accessible TAP that is fully compatible with the
IEEE 1149.1 Standard Test Access Port and Boundary Scan Architecture
. Problems with
testing high-density circuit boards led to the development of this standard under the
sponsorship of the Test Technology Committee of IEEE and the JTAG. The DSP56300 core
implementation supports circuit-board test strategies based on this standard. The test logic
includes a TAP with four dedicated signals, a 16-state controller, and three test data registers.
A boundary scan register links all device signals into a single shift register. The test logic,
implemented utilizing static logic design, is independent of the device system logic. For
details on the JTAG port, consult the DSP56300 Family Manual.
The OnCE module interacts with the DSP56300 core and its peripherals nonintrusively so that
you can examine registers, memory, or on-chip peripherals. This facilitates hardware and
software development on the DSP56300 core processor. OnCE module functions are
provided through the JTAG TAP signals. For details on the OnCE module, consult the
DSP56300 Family Manual.