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| Z8F082ASJ020EG Datasheet, PDF (198/282 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers | |||
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Z8 Encore! XP® F082A Series
Product Specification
181
Operation
This section describes the interface and modes of operation of the On-Chip Debugger.
OCD Interface
The on-chip debugger uses the DBG pin for communication with an external host. This
one-pin interface is a bidirectional, open-drain interface that transmits and receives data.
Data transmission is half-duplex, in that transmit and receive cannot occur simultaneously.
The serial data on the DBG pin is sent using the standard asynchronous data format
defined in RS-232. This pin creates an interface from the Z8 Encore! XP F082A Series
products to the serial port of a host PC using minimal external hardware.Two different
methods for connecting the DBG pin to an RS-232 interface are displayed in Figure 24
and Figure 25. The recommended method is the buffered implementation displayed in
Figure 25. The DBG pin has a internal pull-up resistor which is sufficient for some appli-
cations (for more details about the pull-up current, see the Electrical Characteristics chap-
ter on page 226). For OCD operation at higher data rates or in noisy systems, an external
pull-up resistor is recommended.
Caution: For operation of the on-chip debugger, all power pins (VDD and AVDD) must be supplied
with power and all ground pins (VSS and AVSS) must be properly grounded. The DBG
pin is open-drain and may require an external pull-up resistor to ensure proper operation.
RS-232 TX
RS-232 RX
RS-232
Transceiver
VDD
Schottky
Diode
10 KOhm
DBG Pin
Figure 24. Interfacing the On-Chip Debuggerâs DBG Pin with an RS-232 Interface; #1 of 2
PS022827-1212
PRELIMINARY
Operation
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