DSP56857 datasheet(53/662 Pages) FREESCALE

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56800E Core Description

5685X Overview, Rev. 4

Freescale Semiconductor

1-21

1.4.11 Enhanced On-Chip Emulation (EOnCE) Module

The Enhanced On-Chip Emulation (EOnCE) module allows user interaction in a debug

environment with the 56800E core and its peripherals. Its capabilities include:

•

Examining registers

•

Memory, or on-chip peripherals

•

Setting breakpoints in memory

•

Stepping or tracing instructions

It provides simple, inexpensive, and speed independent access to the 56800E core for

sophisticated debugging and economical system development. The JTAG port allows access to

the Enhanced OnCE module and through the 5685x device to its target system, retaining debug

control without sacrificing other user accessible on-chip resources. This technique eliminates the

costly cabling and the access to processor pins required by traditional emulator systems. The

Enhanced OnCE interface is fully described in the DSP56800E Reference Manual

(DSP56800ERM).

1.4.12 Clocks

1.4.12.1 On-Chip Clock Synthesis Block

The clock synthesis module generates the clocking for the 5685x family of devices. It generates

the master clock used by the System Integration Module (SIM) to derive the system and

peripheral clocks. It also generates the time of day clock used by time-based modules like TOD

and COP. It contains an oscillator module to apply the clock. It also contains a PLL with the

ability to multiply-up the frequency. The PLL can also be bypassed and scaled to lower power

consumption on the 5685x device. The CGM module selects which clock is routed to the master

clock output. It also selects and configures the time of day clock prescaler and PLL.

1.4.12.2 Oscillator

The 5685x device is clocked either from an external crystal or external clock input:

•

Crystal oscillator uses a 2 - 4MHz crystal

•

Ceramic resonator can be used in place of the crystal

•

There are separate power and ground for the oscillator and PLL

•

Oscillator input can be directly clocked at up to 240MHz

DSP56857 датащи(PDF) 53 Page - Freescale Semiconductor, Inc