MC68331
OVERVIEW
MOTOROLA
USER’S MANUAL
3-9
3
Data Strobe
DS
During a read cycle, indicates when it is possible for an external
device to place data on the data bus. During a write cycle,
indicates that valid data is on the data bus.
Data and Size Acknowledge
DSACK[1:0]
Provide asynchronous data transfers and dynamic bus sizing
Development Serial In, Out, Clock
DSI, DSO,
DSCLK
Serial I/O and clock for background debugging mode
Crystal Oscillator
EXTAL, XTAL Connections for clock synthesizer circuit reference; a crystal or an
external oscillator can be used
Function Codes
FC[2:0]
Identify processor state and current address space
Freeze
FREEZE
Indicates that the CPU has entered background mode
Halt
HALT
Suspend external bus activity
Input Capture
IC[3:1]
When a specified transition is detected on an input capture pin, the
value in an internal GPT counter is latched
Input Capture 4/
Output Compare 5
IC4/OC5
Can be configured for either an input capture or output compare
Instruction Pipeline
IPIPE, IFETCH Indicate instruction pipeline activity
Interrupt Request Level
IRQ[7:1]
Provides an interrupt priority level to the CPU
Master In Slave Out
MISO
Serial input to QSPI in master mode; serial output from QSPI in
slave mode
Clock Mode Select
MODCLK
Selects the source and type of system clock
Master Out Slave In
MOSI
Serial output from QSPI in master mode; serial input to QSPI in
slave mode
Output Compare
OC[5:1]
Change state when the value of an internal GPT counter matches
a value stored in a GPT control register
Pulse Accumulator Input
PAI
Signal input to the pulse accumulator
Port C
PC[6:0]
SIM digital output port signals
Auxiliary Timer Clock Input
PCLK
External clock dedicated to the GPT
Peripheral Chip Select
PCS[3:0]
QSPI peripheral chip selects
Port E
PE[7:0]
SIM digital I/O port signals
Port F
PF[7:0]
SIM digital I/O port signals
Port GP
PGP[7:0]
GPT digital I/O port signals
Port QS
PQS[7:0]
QSM digital I/O port signals
Pulse-Width Modulation
PWMA, PWMB Output for PWM
Quotient Out
QUOT
Provides the quotient bit of the polynomial divider
Reset
RESET
System reset
Read-Modify-Write Cycle
RMC
Indicates an indivisible read-modify-write instruction
Read/Write
R/W
Indicates the direction of data transfer on the bus
SCI Receive Data
RXD
Serial input to the SCI
QSPI Serial Clock
SCK
Clock output from QSPI in master mode; clock input to QSPI in
slave mode
Size
SIZ[1:0]
Indicates the number of bytes to be transferred during a bus cycle
Slave Select
SS
Causes serial transmission when QSPI is in slave mode; causes
mode fault in master mode
Three-State Control
TSC
Places all output drivers in a high-impedance state
SCI Transmit Data
TXD
Serial output from the SCI
External Filter Capacitor
XFC
Connection for external phase-locked loop filter capacitor
Table 3-5 Signal Function (Continued)
Signal Name
Mnemonic
Function