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MC68331
USER’S MANUAL
SYSTEM INTEGRATION MODULE
MOTOROLA
4-41
4
4.6.5 Pin State During Reset
It is important to keep the distinction between pin function and pin electrical state clear.
Although control register values and mode select inputs determine pin function, a pin
driver can be active, inactive or in high-impedance state while reset occurs. During
power-up reset, pin state is subject to the constraints discussed in
4.6.7 Power-On
Reset
.
NOTE
Pins that are not used should either be configured as outputs, or (if
configured as inputs) pulled to the appropriate inactive state. This de-
creases additional I
DD
caused by digital inputs floating near mid-sup-
ply level.
4.6.5.1 Reset States of SIM Pins
Generally, while RESET is asserted, SIM pins either go to an inactive high-impedance
state or are driven to their inactive states. After RESET is released, mode selection
occurs, and reset exception processing begins. Pins configured as inputs during reset
become active high-impedance loads after RESET is released. Inputs must be driven
to the desired active state. Pull-up or pull-down circuitry may be necessary. Pins con-
figured as outputs begin to function after RESET is released.
Table 4-18
is a summary
of SIM pin states during reset.
Table 4-17 Module Pin Functions
Module
CPU32
Pin Mnemonic
DSI/IFETCH
DSO/IPIPE
BKPT/DSCLK
PGP7/IC4/OC5
PGP[6:3]/OC[4:1]
PGP[2:0]/IC[3:1]
PAI
PCLK
PWMA, PWMB
PQS7/TXD
PQS[6:4]/PCS[3:1]
PQS3/PCS0/SS
PQS2/SCK
PQS1/MOSI
PQS0/MISO
RXD
Function
DSI/IFETCH
DSO/IPIPE
BKPT/DSCLK
Discrete Input
Discrete Input
Discrete Input
Discrete Input
Discrete Input
Discrete Output
Discrete Input
Discrete Input
Discrete Input
Discrete Input
Discrete Input
Discrete Input
RXD
GPT
QSM