Z8F1680SH020SG Datasheet, PDF (323/412 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F1680 Series
Product Specification
298
• Voltage Brown-Out reset
• Asserting the RESET pin Low to initiate a Reset
• Driving the DBG pin Low when the device is in STOP Mode initiates a System Reset
23.2.2. OCD Data Format
The On-Chip Debugger (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 59).
ST _{D0 D1 D2 D3 D4 D5 D6 D7 SP}
ST = Start bit
SP = Stop bit
D0–D7 = Data bits
Figure 59. OCD Data Format
23.2.3. OCD Autobaud Detector/Generator
To run over a range of baud rates (bits per second) with various system clock frequencies,
the On-Chip Debugger has an Autobaud 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 Autobaud Detector measures this period and sets the OCD Baud Rate Gen-
erator accordingly.
The Autobaud Detector/Generator is clocked by the system clock. The minimum baud rate
is the system clock frequency divided by 512. If the data can be synchronized with the sys-
tem clock, the autobaud generator can run as high as the system clock frequency (1 clock/
bit). The maximum recommended baud rate is the system clock frequency divided by 8.
Table 162 lists the minimum and recommended maximum baud rates for sample crystal
frequencies.
PS025015-1212
PRELIMINARY
On-Chip Debugger