MC68HC711xxxx Motorola, MC68HC711xxxx Datasheet - Page 213

• Manufacturer Part Number: MC68HC711xxxx
• Description: Microcontrollers
• Manufacturer: Motorola

AN1060 — Rev. 1.0
MOTOROLA
pins during reset, the selected mode, and the state of the MDA, SMOD,
and RBOOT control bits. Refer to the composite memory map and
information in
The MDA control bit is determined by the state of the MODA pin as the
MCU leaves reset. MDA selects between single-chip and expanded
operating modes. When MDA is 0, a single-chip mode is selected, either
normal single-chip mode or special bootstrap mode. When MDA is 1, an
expanded mode is selected, either normal expanded mode or special
test mode.
The SMOD control bit is determined by the inverted state of the MODB
pin as the MCU leaves reset. SMOD controls whether a normal mode or
a special mode is selected. When SMOD is 0, one of the two normal
modes is selected, either normal single-chip mode or normal expanded
mode. When SMOD is 1, one of the two special modes is selected, either
special bootstrap mode or special test mode. When either special mode
is in effect (SMOD = 1), certain privileges are in effect, for instance, the
ability to write to the mode control bits and fetching the reset and
interrupt vectors from $BFxx rather than $FFxx.
The alternate vector locations are achieved by simply driving address bit
A14 low during all vector fetches if SMOD = 1. For special test mode, the
alternate vector locations assure that the reset vector can be fetched
from external memory space so the test system can control MCU
operation. In special bootstrap mode, the small boot ROM is enabled in
the memory map by RBOOT = 1 so the reset vector will be fetched from
this ROM and the bootloader firmware will control MCU operation.
MODB
1
0
0
0
Input Pins
MODA
Table 1
0
0
0
1
Table 1. Mode Selection Summary
for the following discussion.
Normal single chip
Normal expanded
Special bootstrap
Mode Selected
Special test
RBOOT
Control Bits in HPRIO
0
0
1
0
SMOD
Application Note
0
0
1
1
MDA
0
1
0
1
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