Z8F6421PM020SC Datasheet, PDF (223/299 Pages) Zilog, Inc. – High Performance 8-Bit Microcontrollers Z8 Encore-R 64K Series

Z8 Encore!^® 64K Series
Product Specification
203
A “reset and stop” function can be achieved by writing 81H to this register. A “reset and
go” function can be achieved by writing 41H to this register. If the device is in DEBUG
mode, a “run” function can be implemented by writing 40H to this register.
Table 101. OCD Control Register (OCDCTL)
BITS
7
6
5
4
3
2
FIELD ^{DBGMODE BRKEN DBGACK BRKLOOP}
RESET
0
R/W
R/W
R
1
0
Reserved RST
R/W
DBGMODE—Debug Mode
Setting this bit to 1 causes the device to enter DEBUG mode. When in DEBUG mode, the
eZ8 CPU stops fetching new instructions. Clearing this bit causes the eZ8 CPU to start
running again. This bit is automatically set when a BRK instruction is decoded and Break-
points are enabled. If the Read Protect Option Bit is enabled, this bit can only be cleared
by resetting the device, it cannot be written to 0.
0 = The 64K Series device is operating in Normal mode.
1 = The 64K Series device is in DEBUG mode.
BRKEN—Breakpoint Enable
This bit controls the behavior of the BRK instruction (opcode 00H). By default, Break-
points are disabled and the BRK instruction behaves like a NOP. If this bit is set to 1 and a
BRK instruction is decoded, the OCD takes action dependent upon the BRKLOOP bit.
0 = BRK instruction is disabled.
1 = BRK instruction is enabled.
DBGACK—Debug Acknowledge
This bit enables the debug acknowledge feature. If this bit is set to 1, then the OCD sends
an Debug Acknowledge character (FFH) to the host when a Breakpoint occurs.
0 = Debug Acknowledge is disabled.
1 = Debug Acknowledge is enabled.
BRKLOOP—Breakpoint Loop
This bit determines what action the OCD takes when a BRK instruction is decoded if
breakpoints are enabled (BRKEN is 1). If this bit is 0, then the DBGMODE bit is automat-
ically set to 1 and the OCD entered DEBUG mode. If BRKLOOP is set to 1, then the eZ8
CPU loops on the BRK instruction.
0 = BRK instruction sets DBGMODE to 1.
1 = eZ8 CPU loops on BRK instruction.
Reserved
These bits are reserved and must be 0.
PS019915-1005
On-Chip Debugger