AN2295 Freescale Semiconductor / Motorola, AN2295 Datasheet - Page 40

• Manufacturer Part Number: AN2295
• Description: Developers Serial Bootloader for M68HC08 and HCS08 MCUs
• Manufacturer: Freescale Semiconductor / Motorola

MCU Slave Software
For improved readability, two timing macros (D_US and D_MS) are used in the code (shown in
;*******************************************************************************************
D_MS:
\@L2:
\@L1:
D_US:
\@L1:
MC68HC908GR
MC68HC908GR MCUs are smaller members of the MC68HC908GP Family that are equipped with ROM
memory with on-chip FLASH programming routines available in the user mode.
MC68HC908GP and MC68HC908GR MCUs are primarily targeted for use with a low-cost 32.768 kHz
crystal. Because the frequency of the crystal is known, no calibration is performed, which saves MCU
memory. Therefore, these MCUs use the
MC68HC908MR
MC68HC908MR MCUs are motor-control oriented members of the M68HC08 Family. The
MC68HC908MR MCUs have no on-chip FLASH programming routines available. Therefore, all FLASH
programming must be done by the bootloader itself.
The MC68HC908MR Family has a PLL (phase-locked loop) circuit that can multiply the crystal frequency.
Typically, a 4-MHz XTAL is used as the reference frequency. This implementation demonstrates how the
PLL circuit is initialized for 8 times the crystal frequency. The source PLL frequency is therefore 32 MHz
and the bus frequency is 8 MHz.
Because the frequency of the crystal is known, no calibration is performed, which saves MCU memory.
Therefore, these MCUs use the
40
MACRO
CLRX
NOP
MACRO
NOP
LDA
DBNZX
DBNZA
ENDM
LDA
DBNZA
ENDM
\1
\@L1
\@L2
\1
\@L1
Developer’s Serial Bootloader for M68HC08 and HCS08 MCUs, Rev. 6
Figure 27. FLASH Programming Macros Source Code
; [2] ||
; [1] ||
; [1] |
; [3] |
; [3] || (1024+4)*(arg-1) + 2 T
; [2]
; [1]
; [3] 4*(arg-1) + 2 T
Known MCU Communication Speed
256*4 = 1024T
Known MCU Communication Speed
method.
method.
Freescale Semiconductor
Figure
27).