Z8 Encore! XP® 4K Series
Product Specification
168
Operation
OCD Interface
The on-chip debugger uses the DBG pin for communication with an external host. This
one-pin interface is a bi-directional, 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® 4K Series prod-
ucts 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 depicted in Figures 24 and 25 . The
recommended method is the buffered implementation depicted in Figure 25. The DBG pin
must always be connected to VDD through an external pull-up resistor.
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 DBGpin is open-drain and must always be connected to VDD through
an external pull-up resistor to insure proper operation.
VDD
RS-232
Transceiver
10KOhm
DBG Pin
Schottky
Diode
RS-232 TX
RS-232 RX
Figure 24.Interfacing the On-Chip Debugger’s DBG Pin with an RS-232 Interface (1)
PS022815-0206
On-Chip Debugger
ZILOG [ ZILOG, INC. ]
