Once Commands And Serial Protocol; Target Site Debug System Requirements - Motorola DSP56305 User Manual

10.10 ONCE COMMANDS AND SERIAL PROTOCOL

To permit an efficient means of communication between the external command
controller and the DSP56300 core chip, the following protocol is adopted. Before starting
any debugging activity, the external command controller has to wait for an acknowledge
on the DE line indicating that the chip has entered the Debug mode (optionally the
external command controller can poll the OS1 and OS0 bits in the JTAG instruction shift
register). The external command controller communicates with the chip by sending 8-bit
commands that can be accompanied by 24 bits of data. Both commands and data are sent
or received Least Significant Bit (LSB) first. After sending a command, the external
command controller should wait for the DSP56300 core chip to acknowledge execution
of the command. The external command controller can send a new command only after
the chip has acknowledged execution of the previous command.
The OnCE commands are classified as follows:
• Read commands (when the chip delivers the required data)
• Write commands (when the chip receives data and writes the data in one of the
OnCE registers)
• Commands that do not have data transfers associated with them
The commands are 8 bits long and have the format shown in Figure 10-4.

10.11 TARGET SITE DEBUG SYSTEM REQUIREMENTS

A typical debug environment consists of a target system where the DSP56300 core-based
device resides in the user defined hardware. The JTAG port interfaces to the external
command controller over a 8-line link consisting of the five JTAG port lines, one OnCE
module line, a ground, and a reset line. The reset line is optional and is only used to reset
the DSP56300 core-based device and its associated circuitry.
The external command controller acts as the medium between the DSP56300 core target
system and a host computer. The external command controller circuit acts as a JTAG
port driver and host computer command interpreter. The controller issues commands
based on the host computer inputs from a user interface program that communicates
with the user.
MOTOROLA DSP56305 User's Manual
On-Chip Emulation Module
OnCE Commands and Serial Protocol
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