ON-CHIP EMULATION (OnCE) PINS
2 - 12
DSP56002 PIN DESCRIPTIONS
MOTOROLA
the DSCK serial clock. Data is always shifted into the OnCE serial port most significant bit
(MSB) first. When the DSI/OS0 pin is an output, it works in conjunction with the OS1 pin
to provide chip status information (see
Section 10 ON CHIP EMULATION (OnCE)
in the
DSP56000 Family Manual
). The DSI/OS0 pin is an output when the processor is not in
debug mode. When switching from output to input, the pin is three-stated. During hard-
ware reset, this pin is defined as an output and it is driven low.
Note:
To avoid possible glitches, an external pull-down resistor should be attached to this pin.
2.3.2
Debug Serial Clock/Chip Status 1 (DSCK/OS1)
The DSCK/OS1 pin supplies the serial clock to the OnCE when it is an input. The serial
clock provides pulses required to shift data into and out of the OnCE serial port. (Data is
clocked into the OnCE on the falling edge and is clocked out of the OnCE serial port on
the rising edge.) The debug serial clock frequency must be no greater than 1/8 of the pro-
cessor clock frequency.
The pin is three-stated when it is changing from input to output. When it is an output, it works
with the OS0 pin to provide information about the chip status (see
SECTION 10 ON CHIP
EMULATION (OnCE)
in the
DSP56000 Family Manual
). It is an output when the chip is not
in debug mode. During hardware reset, this pin is defined as an output and is driven low.
Note:
To avoid possible glitches, an external pull-down resistor should be attached to this pin.
2.3.3
Debug Serial Output (DSO)
The DSP reads serial data from the OnCE through the DSO output pin, as specified by
the last command received from the external command controller. Data is always shifted
out the OnCE serial port most significant bit (MSB) first. Data is clocked out of the OnCE
serial port on the rising edge of DSCK.
The DSO pin also provides acknowledge pulses to the external command controller.
When the chip enters the debug mode, the DSO pin will be pulsed low to indicate (ac-
knowledge) that the OnCE is waiting for commands. After receiving a read command,
the DSO pin 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 receiving
a write command, the DSO pin 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 acknowl-
edge pulse will be provided.
During hardware reset and when the processor is idle, the DSO pin is held high.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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