Z8 Encore! XP® 4K Series
Product Specification
172
2. Wait 5ms for the internal reset sequence to complete.
3. Send the following bytes serially to the debug pin:
DBG← 80H (autobaud)
DBG← EBH
DBG← 5AH
DBG← 70H
DBG← CDH (32-bit unlock key)
4. Release PA2/RESET. The PA0/DBG pin is now identical in function to that of the
DBG pin on the 20-/28-pin device. To enter DEBUG mode, re-autobaud and write
80H to the OCD control register. (See On-Chip Debugger Commands on page 172.)
Breakpoints
Execution Breakpoints are generated using the BRK instruction (opcode 00H). When the
eZ8 CPU decodes a BRK instruction, it signals the On-Chip Debugger. If Breakpoints are
enabled, the OCD enters DEBUG mode and idles the eZ8 CPU. If Breakpoints are not
enabled, the OCD ignores the BRK signal and the BRKinstruction operates as an NOP
instruction.
Breakpoints in Flash Memory
The BRKinstruction is opcode 00H, which corresponds to the fully programmed state of a
byte in Flash memory. To implement a Breakpoint, write 00Hto the required break
address, overwriting the current instruction. To remove a Breakpoint, the corresponding
page of Flash memory must be erased and reprogrammed with the original data.
Runtime Counter
The On-Chip Debugger contains a 16-bit Runtime Counter. It counts system clock cycles
between Breakpoints. The counter starts counting when the On-Chip Debugger leaves
DEBUG mode and stops counting when it enters DEBUG mode again or when it reaches
the maximum count of FFFFH.
On-Chip Debugger Commands
The host communicates to the on-chip debugger by sending OCD commands using the
DBG interface. During normal operation, only a subset of the OCD commands are avail-
able. In DEBUG mode, all OCD commands become available unless the user code and
control registers are protected by programming the Flash Read Protect Option bit (FRP).
The Flash Read Protect Option bit prevents the code in memory from being read out of the
Z8 Encore! XP® 4K Series products. When this option is enabled, several of the OCD
PS022815-0206
On-Chip Debugger
ZILOG [ ZILOG, INC. ]
