Freescale Semiconductor, Inc.
4.2.5.2 PORT B. Port B pins can be independently programmed to function as chip
selects, IRQ≈ and MODCK pins, or discrete I/O pins. These pins are multiplexed as
shown in Figure 4-7. Selection of a pin function is accomplished by a combination of the
port B pin assignment register (PPARB) and the FIRQ bit of the MCR. See Table 4-5 for
port B combinations. By changing the value of the FIRQ bit and the corresponding bits in
the PPARB for a particular signal, the port B pins can be configured for different pin
functions. Upon reset, port B is configured as MODCK, IRQ7, IRQ6, IRQ5, IRQ3, and
CS3–CS0.
MODCK/PORT B0
IRQ7/PORT B7
IRQ6/PORT B6
IRQ5/PORT B5
INTERRUPT
IRQ3/PORT B3
PORT
LOGIC
IRQ4/PORT B4
IRQ2/PORT B2
IRQ1/PORT B1
CS3/IRQ4/PORT B4
CS2/IRQ2/PORT B2
CS1/IRQ1/PORT B1
CS0/AVEC
AVEC
FULL IRQ
MUX
CS3
CS2
CS1
CS0
CHIP-
SELECT
MODULE
FIRQ
Figure 4-7. Full Interrupt Request Multiplexer
Table 4-5. Port B Pin Assignment Register
Pin Function
Signal
FIRQ = 0
PPARB = 0
PORTB7
FIRQ = 0
PPARB = 1
IRQ7
FIRQ = 1
PPARB = 0
PORTB7
FIRQ = 1
PPARB = 1
IRQ7
IRQ7
IRQ6
IRQ5
IRQ3
CS3
PORTB6
PORTB5
PORTB3
CS3
IRQ6
IRQ5
IRQ3
CS3
PORTB6
PORTB5
PORTB3
PORTB4
PORTB2
PORTB1
AVEC
IRQ6
IRQ5
IRQ3
IRQ4
CS2
CS2
IRQ2
CS2
CS1
CS1
IRQ1
CS1
CS0
CS0
AVEC
MODCK
CS0
PORTB0
MODCK
PORTB0
MODCK
NOTE: MODCK has no function after reset.
4- 16
MC68340 USER’S MANUAL
MOTOROLA
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