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| MC68HC05X16 Datasheet, PDF (198/232 Pages) Freescale Semiconductor, Inc – High-density complementary metal oxide semiconductor HCMOS) microcontroller unit | |||
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Freescale Semiconductor, Inc.
B.8
Bootstrap mode
Oscillator divide-by-two is forced in bootstrap mode; all other options stay as programmed in the
mask options register (see Section B.7).
The bootstrap ï¬rmware is located in mask ROM at address locations $0200 to $024F, $03B0 to
$3FFF, $7E00 to $7FDD and $7FE0 to $7FEF. This ï¬rmware can be used to program the EPROM
and the EEPROM, to check if the EPROM is erased, or to load and execute routines in RAM.
After reset, while going to the bootstrap mode, the vector located at address $7FEE and $7FEF
(RESET) is fetched to start execution of the bootstrap program. To place the part in bootstrap
mode, the following conditions must be met during transition of the RESET pin from low to high:
1) IRQ pin at 2xVDD or MDS pin at VDD
2) TCAP1 pin at VDD
3) TCAP2 pin at VSS
The hold time on the IRQ, MDS, TCAP1 and TCAP2 pins is two clock cycles after the external
RESET pin is brought high.
When the MC68HC705X32 is placed in the bootstrap mode, the bootstrap reset vector will be
fetched and the bootstrap ï¬rmware will start to execute. Table B-5 shows the conditions required
to enter each level of bootstrap mode on the rising edge of RESET.
The bootstrap program ï¬rst copies part of itself into RAM (except âRAM parallel loadâ), as the
program cannot be executed in ROM during veriï¬cation/programming of the EPROM.
Table B-5 Mode of operation selection
MDS
IRQ TCAP1
VSS AND VSS to VDD VSS to VDD
VDD OR 2VDD
VDD
VDD OR 2VDD
VDD
VDD OR 2VDD
VDD
VDD OR 2VDD
VDD
VDD OR 2VDD
VDD
VDD OR 2VDD
VDD
x = Donât care
TCAP2
x
VSS
VSS
VSS
VSS
VSS
VSS
PD1 PD2 PD3 PD4
Mode
x x x x Single-chip mode
Bootstrap mode:
0 0 0 x EPROM erase check
1
0
0
x
EPROM erase check, erase EEPROM, parallel
EPROM/EEPROM program/verify
0 1 0 x Parallel EEPROM only verify (SEC bit not active)
1
1
0
x
EPROM erase check, erase EEPROM, parallel EPROM
only program/verify
x 1 1 0 Jump to RAM $0051 (SEC bit not active)
x x 1 1 Serial RAM load and execute (SEC bit not active)
15
MC68HC705X32
MC68HC05X16
For More Information On This Product,
Rev. 1
Go to: www.freescale.com
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