Z8 Encore!® Motor Control Flash MCUs
Product Specification
244
ST
D0
D1
D2
D3
D4
D5
D6
D7
SP
ST = Start Bit
SP = Stop Bit
D0—D7 = Data Bits
Figure 44. OCD Data Format
OCD Auto-Baud Detector/Generator
To run over a range of baud rates (bits per second) with various system clock frequencies,
the On-Chip Debugger has an Auto-Baud Detector/Generator. After a reset, the OCD is
idle until it receives data. The OCD requires that the first character sent from the host is
the character 80h. The character 80hcontains eight continuous bits Low (one Start bit
plus 7 data bits). The Auto-Baud Detector measures this period and sets the OCD Baud
Rate Generator accordingly.
The Auto-Baud Detector/Generator is clocked by the system clock. The minimum baud
rate is the system clock frequency divided by 512. The maximum recommended baud rate
is the system clock frequency divided by 8. Table 133 lists minimum and recommended
maximum baud rates for sample crystal frequencies.
Table 133. OCD Baud-Rate Limits
System Clock
Frequency
Maximum Asynchronous
Baud Rate (bits/s)
Minimum
Baud Rate (bits/s)
20.0MHz
1.0MHz
2.5M
125K
4096
39.1K
1960
64
32.768KHz
If the OCD receives a Serial Break (ten or more continuous bits Low) the Auto-Baud
Detector/Generator resets. The Auto-Baud Detector/Generator can then be reconfigured
by sending 80h. If the Auto-Baud Detector overflows while measuring the Auto-Baud
character, the Auto-Baud Detector will remain reset.
OCD Serial Errors
The On-Chip Debugger can detect any of the following error conditions on the DBG pin:
•
•
Serial Break (a minimum of ten continuous bits Low)
Framing Error (received STOP bit is Low)
On-Chip Debugger
P R E L I M I N A R Y
PS024604-1005
ZILOG [ ZILOG, INC. ]
