Operating Modes and Memory
MC68HC711D3 Data Sheet, Rev. 2.1
22
Freescale Semiconductor
If this mode is entered out of reset, the EPROM is located at $7000–$7FFF and vector accesses are from
external memory. To be in expanded-multiplexed mode with EPROM located at $F000–$FFFF, it is
necessary to start in single-chip mode, executing out of EPROM, and then set the MDA bit of the HPRIO
register to switch mode.
NOTE
R/W, AS, and the high-order address bus (port B) are inputs in single-chip
mode. These inputs may need to be pulled up so that off-chip accesses
cannot occur while the MCU is in single-chip mode.
2.2.3 Special Bootstrap Mode (BOOT)
This special mode is similar to single-chip mode. The resident bootloader program contains a 256-byte
program in a special on-chip read-only memory (ROM). The user downloads a small program into
on-board RAM using the SCI port. Program control is passed to RAM when an idle line of at least four
characters occurs. In this mode, all interrupt vectors are mapped to RAM (see
Table 2-2), so that the user
can set up a jump table, if desired.
Bootstrap mode (BOOT) is entered out of reset if the voltage level on both MODA and MODB is low. The
programming aspect of bootstrap mode, used to program the one-time programmable ROM (OTPROM)
through the MCU, is entered automatically if IRQ is low and programming voltage is available on the VPP
pin. IRQ should be pulled up while in reset with MODA and MODB configured for bootstrap mode to
prevent unintentional programming of the EPROM.
This versatile mode (BOOT) can be used for test and diagnostic functions on completed modules and for
programming the on-board PROM. The serial receive logic is initialized by software in the bootloader
ROM, which provides program control for the SCI baud rate and word format. Mode switching to other
modes can occur under program control by writing to the SMOD and MDA bits of the HPRIO register. Two
special bootloader functions allow either an immediate jump-to-RAM at memory address $0000 or an
immediate jump-to-EPROM at $F000.
Table 2-2. Bootstrap Mode Jump Vectors
Address
Vector
00C4
SCI
00C7
SPI
00CA
Pulse accumulator input edge
00CD
Pulse accumulator overflow
00D0
Timer overflow
00D3
Timer output compare 5/input capture 4
00D6
Timer output compare 4
00D9
Timer output compare 3
00DC
Timer output compare 2
00DF
Timer output compare 1
00E3
Timer input capture 3
00E5
Timer input capture 2
00E8
Timer input capture 1