Z8F0113HJ005EG Datasheet, PDF (172/245 Pages) Zilog, Inc. – High-Performance 8-Bit Microcontrollers

Z8 Encore! XP^® F0823 Series
Product Specification
157
Operation
The following section describes the operation of the OCD.
OCD Interface
The OCD uses the DBG pin for communication with an external host. This one-pin inter-
face is a bidirectional open-drain interface that transmits and receives data. Data transmis-
sion 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 F0823 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 23 and Figure 24. The recommended
method is the buffered implementation depicted in Figure 24. The DBG pin has a internal
pull-up resistor which is sufficient for some applications (for more details about the pull-
up current, see the Electrical Characteristics chapter on page 196). For OCD operation at
higher data rates or in noisy systems, Zilog recommends an external pull-up resistor.
Caution: For operation of the OCD, all power pins (V_DD and AV_DD) must be supplied with power,
and all ground pins (V_SS and AV_SS) 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 k
DBG Pin
Figure 23. Interfacing the On-Chip Debugger’s DBG Pin with an RS-232 Interface, # 1 of 2
PS024315-1011
PRELIMINARY
Operation