Specifications

FC protocol description
Developer’s Serial Bootloader, Rev. 13
Freescale Semiconductor 5
characters can be interpreted differently instead of original 0xFC sent out by the PC (Figure 3). The 0xFC
pattern check on the MCU side can be eliminated completely, which saves MCU memory.
Figure 3. Matching different communication speeds
The following table shows the characters that can be correctly received (without framing or noise errors)
if transmit and receive speeds are not equal:
.
Table 1. PC to MCU transmission — unmatched data rate
PC Data Rate MCU Data Rate
Character
Received
in Binary
Character
Received
in Hex
9600 9600*1/3 11111111b 0xFF
9600 9600*2/3 11111110b 0xFE
9600 9600*3/3 11111100b 0xFC
9600 9600*4/3 11111000b 0xF8
9600 9600*5/3 11110000b 0xF0
9600 9600*6/3 11100000b 0xE0
9600 9600*7/3 11000000b 0xC0
9600 9600*8/3 10000000b 0x80
9600 9600*9/3 00000000b 0x00
D0 D1 D2 D3 D4
D5 D6
D7 STOP
START
IDLE
BOTH MCU AND PC
DATA RATES ARE EQUAL
MCU RECEIVES 0XFC
MCU CLOCK IS
3 TIMES FASTER
MCU RECEIVES 0X00
MCU CLOCK IS
3 TIMES SLOWER
MCU RECEIVES 0XFF
TIME
D0 D1 D2 D3 D4 D5 D6 D7
STOP
START
IDLE
D0 D1START
IDLE
PC TRANSMITS 0XFC CHARACTER AT PROPER DATA RATE: