
MC68HC05X16
Rev. 1
MC68HC705X32
15
B.8
Bootstrap mode
Oscillator divide-by-two is forced in bootstrap mode; all other options stay as programmed in the
The bootstrap rmware is located in mask ROM at address locations $0200 to $024F, $03B0 to
$3FFF, $7E00 to $7FDD and $7FE0 to $7FEF. This 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 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 rst copies part of itself into RAM (except ‘RAM parallel load’), as the
program cannot be executed in ROM during verication/programming of the EPROM.
Table B-5 Mode of operation selection
MDS
IRQ
TCAP1
TCAP2
PD1 PD2 PD3 PD4
Mode
VSS AND VSS to VDD VSS to VDD
x
xxxx
Single-chip mode
Bootstrap mode:
VDD
OR
2VDD
VDD
VSS
0
x
EPROM erase check
VDD
OR
2VDD
VDD
VSS
100
x
EPROM erase check, erase EEPROM, parallel
EPROM/EEPROM program/verify
VDD
OR
2VDD
VDD
VSS
0
1
0
x
Parallel EEPROM only verify (SEC bit not active)
VDD
OR
2VDD
VDD
VSS
110
x
EPROM erase check, erase EEPROM, parallel EPROM
only program/verify
VDD
OR
2VDD
VDD
VSS
x
1
0
Jump to RAM $0051 (SEC bit not active)
VDD
OR
2VDD
VDD
VSS
x
1
Serial RAM load and execute (SEC bit not active)
x = Don’t care
196
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com