Z8FMC16100 Series Flash MCU
Product Specification
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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
Auto-Baud 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 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
Z8FMC16100 Series Flash MCU device or when recovering from an error. A Serial Break
from the host resets the Auto-Baud Generator/Detector but does not reset the OCD Con-
trol 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.
Automatic Reset
The Z8FMC16100 Series Flash MCU devices have the capability to switch clock sources
during operation. If the Auto-Baud is set and the clock source is switched, the Auto-Baud
value becomes invalid. A new Auto-Baud value must be configured with the new clock
frequency.
The oscillator control logic has clock switch detection. If a clock switch is detected and
the Auto-Baud is set, the device will automatically send a Serial Break for 4096 clocks.
This will reset the Auto-Baud and indicate to the host that a new Auto-Baud character
should be sent.
Break Points
Execution break points are generated using the BRK instruction (Op Code 00h). When the
eZ8 CPU decodes a BRK instruction, it signals the On-Chip Debugger. If break points are
enabled, the OCD idles the eZ8 CPU and enters DEBUG mode. If break points are not
enabled, the OCD ignores the BRK signal and the BRK instruction operates as a NOP
instruction.
If break points are enabled, the OCD can be configured to automatically enter DEBUG
mode, or to loop on the break instruction. If the OCD is configured to loop on the BRK
instruction, then the CPU remains able to service DMA and interrupt requests.
The loop on BRK instruction can service interrupts in the background. For interrupts to be
serviced in the background, there cannot be any break points in the interrupt service rou-
tine. Otherwise, the CPU stops on the break point in the interrupt routine. For interrupts to
be serviced in the background, interrupts must also be enabled. Debugging software does
not automatically enable interrupts when using this feature. Interrupts are typically dis-
PS024604-1005
P R E L I M I N A R Y
Automatic Reset
ZILOG [ ZILOG, INC. ]
