Reset
MPC885 PowerQUICC Family Reference Manual, Rev. 2
11-6
Freescale Semiconductor
11.3
MPC885 Reset Configuration
When a hard reset event occurs, the MPC885 reconfigures both its internal hardware and the development
port. A soft reset is used to reconfigure the development port without changing the MPC885’s internal
machine state. The following sections describe the configuration of the MPC885 using hard and soft reset
events.
11.3.1
Hard Reset
When a hard reset event occurs, the MPC885 determines its initial mode of operation by sampling the
values present on the data bus (D[0–31]) or from an internal default constant (D[0–31] = 0x00000000). If
the RSTCONF signal is asserted at sampling time, the configuration is sampled from the data bus. If the
RSTCONF signal is negated the internal default value is selected. While HRESET and RSTCONF are
asserted, the MPC885 weakly pulls the data bus low, and the desired configuration is selected by driving
the appropriate bits high as shown in
Figure 11-4
.
Figure 11-4
shows a typical data bus configuration input circuit.
Figure 11-4. Data Bus Configuration Input Circuit
7
JTRS
JTAG reset status. Cleared by a power-on reset. When the JTAG reset request is set, this bit is
set and remains set until software clears it.
0 No JTAG reset event occurred.
1 A JTAG reset event occurred.
8–31
—
Reserved, should be cleared.
Table 11-2. Reset Status Register Bit Settings (continued)
Bits
Name
Description
NOTE: The value of the internal pull-down resistor is not specified or guaranteed.
MUX
DX (Data Line)
Configuration
Word
HRESET
RSTCONF
MPC860
MPC885
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