Typewriter User Manual

MOTOROLA MC68340 USER’S MANUAL 4- 35
4.3.5.5 PORT B PIN ASSIGNMENT REGISTER (PPARB). PPARB controls the function
of each port B pin. Any set bit defines the corresponding pin to be an
IRQ≈ input or CS≈
as defined in Table 4-5. Any cleared bit defines the corresponding pin to be a discrete I/O
pin (or
CS≈ if the FIRQ bit of the MCR is zero) controlled by the port B data and data
direction registers. The MODCK signal has no function after reset. PPARB is configured to
all ones at reset to provide for MODCK,
IRQ7, IRQ6, IRQ5, IRQ3, and CS3–CS0. This
register can be read or written at any time.
PPARB $01F
76543210
PPARB7
(IRQ7)
PPARB6
(IRQ6)
PPARB5
(IRQ5)
PPARB4
(IRQ4)
PPARB3
(IRQ3)
PPARB2
(IRQ2)
PPARB1
(IRQ1)
PPARB0
(MODCK)
RESET:
11111111
Supervisor Only
4.3.5.6 PORT B DATA DIRECTION REGISTER (DDRB). DDRB controls the direction of
the pin drivers when the pins are configured as I/O. Any set bit configures the
corresponding pin as an output; any cleared bit configures the corresponding pin as an
input. This register affects only pins configured as discrete I/O. This register can be read
or written at any time.
DDRB $01D
76543210
DD7 DD6 DD5 DD4 DD3 DD2 DD1 DD0
RESET:
00000000
Supervisor/User
4.3.5.7 PORT B DATA REGISTER (PORTB, PORTB1). This is a single register that can
be accessed at two different addresses. This register affects only those pins configured as
discrete I/O. A write is stored in the internal data latch, and if any port B pin is configured
as an output, the value stored for that bit is driven on the pin. A read of this register
returns the value stored in the register only if the pin is configured as a discrete output.
Otherwise, the value read is the value of the pin. This register can be read or written at
any time.
PORTB, PORTB1 $019, 01B
76543210
P7 P6 P5 P4 P3 P2 P1 P0
RESET:
UUUUUUUU
Supervisor/User
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cale Semiconductor,
I
Freescale Semiconductor, Inc.
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