AN2295 Freescale Semiconductor / Motorola, AN2295 Datasheet - Page 5

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

Table 1
transmit and receive speeds are not equal.
Freescale Semiconductor
BOTH MCU AND PC
DATA RATES ARE EQUAL
MCU CLOCK IS
3 TIMES FASTER
MCU CLOCK IS
3 TIMES SLOWER
shows the characters that can be correctly received (i.e., without framing or noise errors) if
PC TRANSMITS 0XFC CHARACTER AT PROPER DATA RATE:
PC Data Rate
Table 1. PC to MCU Transmission — Unmatched Data Rate
9600
9600
9600
9600
9600
9600
9600
9600
9600
Developer’s Serial Bootloader for M68HC08 and HCS08 MCUs, Rev. 6
Figure 3. Matching Different Communication Speeds
TIME
IDLE
IDLE
MCU Data Rate
9600*1/3
9600*2/3
9600*3/3
9600*4/3
9600*5/3
9600*6/3
9600*7/3
9600*8/3
9600*9/3
START
START
D0
D1
11111111b
11111110b
11111100b
11111000b
11110000b
11100000b
11000000b
10000000b
00000000b
Character
Received
in Binary
D2
D3
D0
MCU RECEIVES 0XFC
D4
MCU RECEIVES 0XFF
MCU RECEIVES 0X00
Character
Received
D5
in Hex
$FF
$FE
$FC
$F8
$F0
$E0
$C0
$80
$00
D6
FC Protocol Description
D1
D7
STOP
5