Alternate Pin Functions
D-2
MC68322 USER’S MANUAL
MOTOROLA
D.2 STATE DURING RESET
The output pins are in the normal deasserted state during reset and the first bus cycles,
except for A[21:25], AS, and RAS[4:5]. Pins A[22:25] may be used as inputs on systems
that require 4M or less of ROM by using the input pin mode as described below.
D.3 REGISTERS
The new registers in the table below control the alternate pin function.
The following bits have been added to the existing external interrupt registers—DREQ
(EXIR2) bits were added to the EXIR0 registers and BR (EXIR3) bits were added to the
EXIR1 registers. The new bits are located immediately adjacent to the bits already contained
in those registers. For example, the EXIR0 enable bit is bit 0 in the EXIR0 ENB register and
the EXIR2 enable bit is bit 1. Similarly, the EXIR0 status and request bits are bit 1 and 0 of
the EXIR0 EVENT register, respectively, and the EXIR2 status and request bits are bit 3
and 2, respectively. EXIR0 and EXIR2 will share the same interrupt level as EXIR1 and
EXIR3. If BR or DREQ are to be used as simple inputs rather than interrupts, the software
should keep the interrupts disabled. Users can check the input pin status by reading the
status bit for the corresponding pin in the appropriate external interrupt event register. In a
similar way, the IRQ0 and IRQ1 pins have always been available as input pins.
REGISTER
ADDRESS
BITS
R/W
DESCRIPTION
ALTPIN SEL
00FFF910
16
R/W
Select Alternate Function For Each Pin.
ALTPIN DIR
00FFF912
4
R/W
Direction Control For A[22:25], 0=In, 1=Out.
ALTPIN IN
00FFF914
4
R
Input Status For A[22:25].
ALTPIN OUT
00FFF916
15
R/W
Output Control For Output Bits.
REGISTER
ADDRESS
BITS
R/W
DESCRIPTION
EXIR0 ENB
00FFF770
1
R/W
Interrupt EXIR2 Enable.
EXIR0 EVENT
00FFF772
2
R/W
Interrupt EXIR2 Request And Status.
EXIR0 MODE
00FFF776
2
R/W
Interrupt EXIR2 Mode.
EXIR0 SEN
00FFF778
1
R/W
Interrupt EXIR2 Software Enable Bit.
EXIR1 ENB
00FFF780
1
R/W
Interrupt EXIR3 Enable.
EXIR1 EVENT
00FFF782
2
R/W
Interrupt EXIR3 Request And Status.
EXIR1 MODE
00FFF786
2
R/W
Interrupt EXIR3 Mode.
EXIR1 SEN
00FFF788
1
R/W
Interrupt EXIR3 Software Enable Bit.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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