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584
Notes on Use of User Mode:
When the chip comes out of reset in boot mode, it measures the low period of the input at the
SCI’s RxD1 pin. The reset should end with RxD1 high. After the reset ends, it takes about
100 states for the chip to get ready to measure the low period of the RxD1 input.
In boot mode, if any data has been programmed into the flash memory (if all data is not 1),
all flash memory blocks are erased. Boot mode is for use when user program mode is
unavailable, such as the first time on-board programming is performed, or if the program
activated in user program mode is accidentally erased.
Interrupts cannot be used while the flash memory is being programmed or erased.
The RxD1 and TxD1 pins should be pulled up on the board.
Before branching to the programming control program (RAM area H'(FF)E080 (128-kbyte
versions) or H'(FF)E880 (64-kbyte versions)), the chip terminates transmit and receive
operations by the on-chip SCI (channel 1) (by clearing the RE and TE bits in SCR to 0), but
the adjusted bit rate value remains set in BRR. The transmit data output pin, TxD1, goes to
the high-level output state (P84DDR = 1, P84DR = 1).
The contents of the CPU’s internal general registers are undefined at this time, so these
registers must be initialized immediately after branching to the programming control
program. In particular, since the stack pointer (SP) is used implicitly in subroutine calls, etc.,
a stack area must be specified for use by the programming control program.
The initial values of other on-chip registers are not changed.
Boot mode can be entered by making the pin settings shown in table 21.6 and executing a
reset-start.
When the chip detects the boot mode setting at reset release*
1, P92, P91, and P90 can be
used as I/O ports.
Boot mode can be cleared by driving the reset pin low, waiting at least 20 states, then setting
the mode pins, and executing reset release*
1. Boot mode can also be cleared by a WDT
overflow reset.
The mode pin input levels must not be changed in boot mode.
If the mode pin input levels are changed (for example, from low to high) during a reset, the
state of ports with multiplexed address functions and bus control output pins (
$6, 5', :5)
will change according to the change in the microcomputer’s operating mode*
2.
Therefore, care must be taken to make pin settings to prevent these pins from becoming
output signal pins during a reset, or to prevent collision with signals outside the
microcomputer.
Notes: 1. Mode pin input must satisfy the mode programming setup time (t
MDS = 4 states) with
respect to the reset release timing.
2. Ports with multiplexed address functions will output a low level as the address signal
if mode pin setting is for mode 1 is entered during a reset. In other modes, the port
pins go to the high-impedance state. The bus control output signals will output a high