MPC555
/
MPC556
SIGNAL DESCRIPTIONS
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
2-32
2.4.7 Special Pull Resistor Disable Control (SPRDS)
For the pins that support debug and opcode-tracking functionality, the pull-up and pull-
down resistors are controlled by the SPRDS signal, which is somewhat like the encod-
ed 3-V / 5-V select. During reset this signal is used synchronously to enable the pull-
up resistors in the pads. On negation of reset, based on which functionality is selected
for the pins, this signal is set to disable the pull-up resistors or remains held in its reset
state to indicate that the pull-ups are disabled only when the output driver is enabled.
For example, if a pin is configured as a bus arbitration pin, The SPRDS signal remains
low throughout reset. This causes the pull-up to be enabled. When reset is released,
SPRDS remains low. The output enable for the driver is negated by default. When the
output driver is enabled, the pull-up is disabled.
When a pin is configured as an opcode-tracking or debug pin, SPRDS remains low
throughout reset. This causes the pull-up to be enabled. When reset is released,
SPRDS is asserted. This disables the pull-up resistor immediately. The output driver
drives the pin to the required state after reset.
2.4.8 Pin Reset States
summarizes the reset states of all the pins on the MPC555
/
MPC556.
Table 2-4 Pin Reset State
Pin
Function
Port
Voltage
Reset State
USIU
ADDR[8:31]/
SGPIOA[8:31]
ADDR[8:31]
I/O
3 V
PU5 until reset negates
1
SGPIOA[8:31]
IO
5 V
PU5 until PRDS is set
DATA[0:31]/
SGPIOD[0:31]
DATA[0:31]
I/O
3 V
PD until reset negates
SGPIOD[0:31]
I/O
5 V
PD until PRDS is set
IRQ[0]/SGPIOC[0]
IRQ[0]
I
3 V
PU5 until reset negates
1
SGPIOC[0]
I/O
5 V
PU5 until PRDS is set
IRQ[1]/
RSV/SGPIOC[1]
IRQ[1]
I
3 V
PU5 until reset negates
1
RSV
O
3 V
PU5 until reset negates
1
SGPIOC[1]
I/O
5 V
PU5 until PRDS is set
IRQ[2]/
CR/SGPIOC[2]/
MTS
IRQ[2]
I
3 V
PU5 until reset negates
1
CR
I
3 V
PU5 until reset negates
1
SGPIOC[2]
I/O
5 V
PU5 until PRDS is set
MTS
O
3 V
PU5 until PRDS negates
IRQ[3]/
KR, RETRY/
SGPIOC[3]
IRQ[3]
I
3 V
PU5 until reset negates
1
KR, RETRY
I/O
3 V
PU5 when driver not enabled
2
SGPIOC[3]
I/O
5 V
PU5 until PRDS is set
IRQ[4]/
AT[2]/
SGPIOC[4]
IRQ[4]
I
3 V
PU5 until reset negates
1
AT[2]
O
3 V
PU5 until reset negates
1
SGPIOC[4]
I/O
5 V
PU5 until PRDS is set
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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