ZUSBOPTSC01ZAC datasheet(266/402 Pages) ZILOG

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On-Chip Debugger

P R E L I M I N A R Y

PS024604-1005

Z8 Encore!® Motor Control Flash MCUs

Product Specification

244

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 80h contains 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.

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)

Figure 44. OCD Data Format

Table 133. OCD Baud-Rate Limits

System Clock

Frequency

Maximum Asynchronous

Baud Rate (bits/s)

Minimum

Baud Rate (bits/s)

20.0MHz

2.5M

39.1K

1.0MHz

125K

1960

32.768KHz

4096

ST = Start Bit

SP = Stop Bit

D0—D7 = Data Bits

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