Operating Modes and On-Chip Memory
Data Sheet
M68HC11E Family — Rev. 5
46
Operating Modes and On-Chip Memory
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MOTOROLA
A normal mode is selected when MODB is logic 1 during reset. One of three reset
vectors is fetched from address $FFFA–$FFFF, and program execution begins
from the address indicated by this vector. If MODB is logic 0 during reset, the
special mode reset vector is fetched from addresses $BFFA–$BFFF, and software
has access to special test features. Refer to
Section 5. Resets and Interrupts
.
RBOOT — Read Bootstrap ROM Bit
Valid only when SMOD is set (bootstrap or special test mode); can be written
only in special modes
0 = Bootloader ROM disabled and not in map
1 = Bootloader ROM enabled and in map at $BE00–$BFFF
SMOD and MDA — Special Mode Select and Mode Select A Bits
The initial value of SMOD is the inverse of the logic level present on the MODB
pin at the rising edge of reset. The initial value of MDA equals the logic level
present on the MODA pin at the rising edge of reset. These two bits can be read
at any time. They can be written anytime in special modes. MDA can be written
only once in normal modes. SMOD cannot be set once it has been cleared.
Address:
$103C
Bit 7
6
5
4
3
2
1
Bit 0
Read:
RBOOT
(1)
SMOD
(1)
MDA
(1)
IRV(NE)
(1)
PSEL3
PSEL2
PSEL1
PSEL0
Write:
Resets:
Single chip:
0
0
0
0
0
1
1
0
Expanded:
0
0
1
0
0
1
1
0
Bootstrap:
1
1
0
0
0
1
1
0
Test:
0
1
1
1
0
1
1
0
1. The reset values depend on the mode selected at the RESET pin rising edge.
Figure 2-9. Highest Priority I-Bit Interrupt and Miscellaneous
Register (HPRIO)
Input
Mode
Latched at Reset
MODB
MODA
SMOD
MDA
1
0
Single chip
0
0
1
1
Expanded
0
1
0
0
Bootstrap
1
0
0
1
Special test
1
1
F
Freescale Semiconductor, Inc.
n
.