Typewriter User Manual

4- 16 MC68340 USER’S MANUAL MOTOROLA
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.
INTERRUPT
PORT
LOGIC
FULL IRQ
MUX
AVEC
CHIP-
SELECT
MODULE
CS1/IRQ1/PORT B1
CS3
CS2
CS1
CS0
CS0/AVEC
FIRQ
CS2/IRQ2/PORT B2
CS3/IRQ4/PORT B4
IRQ3/PORT B3
IRQ5/PORT B5
IRQ6/PORT B6
IRQ7/PORT B7
MODCK/PORT B0
IRQ4/PORT B4
IRQ2/PORT B2
IRQ1/PORT B1
Figure 4-7. Full Interrupt Request Multiplexer
Table 4-5. Port B Pin Assignment Register
Pin Function
Signal FIRQ = 0 FIRQ = 0 FIRQ = 1 FIRQ = 1
PPARB = 0 PPARB = 1 PPARB = 0 PPARB = 1
IRQ7
PORTB7 IRQ7 PORTB7 IRQ7
IRQ6
PORTB6 IRQ6 PORTB6 IRQ6
IRQ5
PORTB5 IRQ5 PORTB5 IRQ5
IRQ3
PORTB3 IRQ3 PORTB3 IRQ3
CS3
CS3
CS3 PORTB4 IRQ4
CS2
CS2
CS2 PORTB2 IRQ2
CS1
CS1
CS1 PORTB1 IRQ1
CS0
CS0
CS0 AVEC AVEC
MODCK
PORTB0
MODCK PORTB0 MODCK
NOTE: MODCK has no function after reset.
Frees
cale Semiconductor,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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