Z8F1680SH020SG Datasheet, PDF (325/412 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F1680 Series
Product Specification
300
Device
DBG
CLOCK
High Speed
Adapter
Any high-speed
interface
Host PC
Figure 60. Synchronous Operation
23.2.5. 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)
• Transmit Collision (OCD and host simultaneous transmission detected by the OCD)
When the OCD detects one of these errors, it aborts any command currently in progress,
transmits a Serial Break 4096 system clock cycles long back to the host and resets the
Autobaud Detector/Generator. A Framing Error or Transmit Collision can be caused by
the host sending a Serial Break to the OCD. Because of the open-drain nature of the inter-
face, returning a Serial Break back to the host only extends the length of the Serial Break
if the host releases the Serial Break early.
The host transmits a Serial Break on the DBG pin when first connecting to theZ8 Encore!
XP F1680 Series device or when recovering from an error. A Serial Break from the host
resets the Autobaud Generator/Detector but does not reset the OCD Control Register. A
Serial Break leaves the device in DEBUG mode if that is the current mode. The OCD is
held in Reset until the end of the Serial Break when the DBG pin returns High. Because of
the open-drain nature of the DBG pin, the host can send a Serial Break to the OCD even if
the OCD is transmitting a character.
PS025015-1212
PRELIMINARY
On-Chip Debugger