Z8F0113HJ005EG Datasheet, PDF (175/245 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F0823 Series
Product Specification
160
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 eight. The maximum possible baud rate for asynchronous datastreams is the system
clock frequency divided by four, but this theoretical maximum is possible only for low
noise designs with clean signals. Table 100 lists minimum and recommended maximum
baud rates for sample crystal frequencies.
Table 100. OCD Baud-Rate Limits
System Clock
Frequency (MHz)
5.5296
0.032768 (32 kHz)
Recommended
Maximum Baud Rate
(kbps)
1382.4
4.096
Recommended
Standard PC Baud
Rate (bps)
691,200
2400
Minimum Baud Rate
(kbps)
1.08
0.064
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 80H.
OCD Serial Errors
The OCD detects any of the following error conditions on the DBG pin:
• Serial Break (a minimum of nine 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 four character long Serial Break back to the host, and resets the auto-baud
detector/generator. A Framing Error or Transmit Collision may be caused by the host
sending a Serial Break to the OCD. Because of the open-drain nature of the interface,
returning a Serial Break 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 the F0823 Series
devices or when recovering from an error. A Serial Break from the host resets the auto-
baud 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 sends a Serial Break to the OCD even if the OCD is
transmitting a character.
PS024315-1011
PRELIMINARY
Operation