MC68HC05X16 Datasheet, PDF (26/232 Pages) Freescale Semiconductor, Inc – High-density complementary metal oxide semiconductor HCMOS) microcontroller unit

Freescale Semiconductor, Inc.
2.1.2 Bootstrap mode
2
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 2xV_DD OR MDS pin at V_DD
2) TCAP1 pin at V_DD
3) TCAP2 pin at V_SS
PD4 and PD3 are connected according to the values given in Table 2-1 to select the device’s
function from the following three functions:
• Execute serial RAM loader program
• Jump to RAM + 1
• Jump to any address
If the SEC bit in the option register is set, on first entering bootstrap mode the RAM and the EEPROM
are completely erased. The option register which contains the security bit is erased last, before any
program can be executed. The bootstrap software is implemented in the following locations:
• RAM load and execute from $03B0 to $03FD
• Vectors and program select from $7F80 to $7FEF
ENTRY
SEC bit active?
NO
YES
Save PD in RAM. Erase
whole EEPROM + RAM
and check EPROM +
SEC bit.
PD3 set
NO
?
YES
NO
Reserved for
Motorola use.
PD4 set
?
YES
Jump to address
defined by ports A, B
and C.
PD4 set
NO
?
YES
Jump to RAM + 1.
Serial RAM bootstrap
loader.
Figure 2-1 Bootstrap mode function selection flow chart
MODES OF OPERATION AND PIN DESCRIPTIONS MC68HC05X16
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