z8f083a ZiLOG Semiconductor, z8f083a Datasheet - Page 148

• Manufacturer Part Number: z8f083a
• Description: High-performance 8-bit Microcontrollers
• Manufacturer: ZiLOG Semiconductor

PS026308-1207
START
OCD Data Format
OCD Auto-Baud Detector/Generator
•
•
The OCD interface uses the asynchronous data format defined for RS-232. Each character
is transmitted as 1 start bit, 8 data bits (least-significant bit first), and 1 stop bit. See
Figure
To run over a range of baud rates (data bits per second) with various system clock
frequencies, the On-Chip Debugger contains 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
Start bit plus 7 data bits), framed between high 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. For optimal operation with asynchronous
datastreams, the maximum recommended baud rate is the system clock frequency divided
by 8. The maximum possible baud rate for asynchronous datastreams is the system clock
frequency divided by 4, but this theoretical maximum is possible only for low noise
designs with clean signals.
rates for sample crystal frequencies.
Table 91. OCD Baud-Rate Limits
If the OCD receives a serial break (nine or more continuous bits low), the auto-baud
detector/generator resets. Reconfigure the auto-baud detector/generator by sending
D0
Asserting the RESET pin low to initiate a reset.
Driving the DBG pin low while the device is in STOP mode, initiates a system reset.
Frequency (MHz)
0.032768 (32 kHz)
System Clock
20.
D1
20.0
1.0
D2
Figure 20. OCD Data Format
Table 91
80H
Maximum Baud
Recommended
D3
Rate (kbps)
. The character
2500.0
125.0
4.096
lists minimum and recommended maximum baud
D4
80H
Standard PC Baud
D5
Recommended
has eight continuous bits low (one
Rate (bps)
1,843,200
115,200
2400
Z8 Encore!
D6
Product Specification
D7
®
Minimum Baud
On-Chip Debugger
F083A Series
Rate (kbps)
0.064
1.95
STOP
39
80H
.
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