MC68HC908GT16 Datasheet, PDF (218/412 Pages) Motorola, Inc – Microcontrollers

Monitor ROM (MON)
Table 15-3 lists external frequencies required to achieve a standard
baud rate of 9600 bps. Other standard baud rates can be accomplished
using proportionally higher or lower frequency generators. If using a
crystal as the clock source, be aware of the upper frequency limit that the
internal clock module can handle. See 23.8 5.0-V Control Timing and
23.9 3.0-V Control Timing for this limit.
Table 15-3. Monitor Baud Rate Selection
External
Frequency
4.9152 MHz
9.8304 MHz
9.8304 MHz
IRQ
V_TST
V_TST
V_DD
PTC3
0
1
X
Internal
Frequency
2.4576 MHz
2.4576 MHz
2.4576 MHz
Baud Rate
(bps)
9600
9600
9600
15.4.5 Commands
The monitor ROM firmware uses these commands:
• READ (read memory)
• WRITE (write memory)
• IREAD (indexed read)
• IWRITE (indexed write)
• READSP (read stack pointer)
• RUN (run user program)
The monitor ROM firmware echoes each received byte back to the PTA0
pin for error checking. An 11-bit delay at the end of each command
allows the host to send a break character to cancel the command. A
delay of two bit times occurs before each echo and before READ,
IREAD, or READSP data is returned. The data returned by a read
command appears after the echo of the last byte of the command.
NOTE: Wait one bit time after each echo before sending the next byte.
Technical Data
218
MC68HC908GT16 • MC68HC908GT8 — Rev. 2
Monitor ROM (MON)
MOTOROLA