Motorola DSP56012 - Manual (Page 60)

2-20 DSP56012 User’s Manual MOTOROLA
Signal Descriptions
OnCE Port
DSO Output Pulled
high
Debug Serial Output— Data contained in one of the OnCE
controller registers is provided through the DSO output signal,
as specified by the last command received from the external
command controller. Data is always shifted out the OnCE
serial port MSB first. Data is clocked out of the OnCE serial
port on the rising edge of DSCK.
The DSO signal also provides acknowledge pulses to the
external command controller. When the chip enters the Debug
mode, the DSO signal will be pulsed low to indicate
(acknowledge) that the OnCE is waiting for commands. After
the OnCE receives a read command, the DSO signal will be
pulsed low to indicate that the requested data is available and
the OnCE serial port is ready to receive clocks in order to
deliver the data. After the OnCE receives a write command, the
DSO signal will be pulsed low to indicate that the OnCE serial
port is ready to receive the data to be written; after the data is
written, another acknowledge pulse will be provided.
DR Input Input Debug Request— The debug request input (DR) allows the
user to enter the Debug mode of operation from the external
command controller. When DR is asserted, it causes the DSP to
finish the current instruction being executed, save the
instruction pipeline information, enter the Debug mode, and
wait for commands to be entered from the DSI line. While in
Debug mode, the DR signal lets the user reset the OnCE
controller by asserting it and deasserting it after receiving
acknowledge. It may be necessary to reset the OnCE controller
in cases where synchronization between the OnCE controller
and external circuitry is lost. DR must be deasserted after the
OnCE responds with an acknowledge on the DSO signal and
before sending the first OnCE command. Asserting DR will
cause the chip to exit the Stop or Wait state. Having DR
asserted during the deassertion of RESET will cause the DSP to
enter Debug mode.
Note: If the OnCE interface is not in use, attach an external pull-up
resistor to the DR input.
Table 2-12 On-Chip Emulation Port (OnCE) Signals (Continued)
Signal
Name
Signal
Type
State
during
Reset
Signal Description