Debug Support
e200z3 Power Architecture Core Reference Manual, Rev. 2
9-20
Freescale Semiconductor
The OnCE decoder receives as input the 10-bit command from the OCMD and the status signals from the
processor, and generates all the strobes required for reading and writing the selected OnCE registers.
Single-stepping of instructions is performed by placing the CPU in debug mode, scanning appropriate
information into the CPUSCR, and setting the GO bit (with the EX bit cleared) with the RS field indicating
either the CPUSCR or no register selected. After executing a single instruction, the CPU re-enters debug
mode and awaits further commands. During single-stepping, exception conditions may occur if not
2
EX
Exit. The Exit command is executed only if the Go command is issued and the operation is a read/write to
CPUSCR or a read/write to no register selected. Otherwise, the EX bit is ignored.
The processor leaves debug mode after the TAP controller Update-DR state is entered. Note that if the DR bit in
the OnCE control register is set or remains set, or if a bit in the DBSR is set, or if a bit in the DBSR is set and
DBCR0[EDM] = 1 (external debug mode is enabled), then the processor may return to the debug mode without
execution of an instruction, even though the EX bit was set.
0 Remain in debug mode
1 Leave debug mode. The processor leaves debug mode and resumes normal operation until another debug
request is generated.
3–9
RS
Register select. Defines which register is the source for the read or the destination for the write operation.
indicates the OnCE register addresses. Attempted writes to read-only registers are ignored.
000 0000–000 0001
Reserved
000 0010
JTAG ID read–only
000 0011–000 1111
Reserved
001 0000
CPU scan register CPUSCR
001 0001
No register selected bypass
001 0010
OnCE control register OCR
001 0011–001 1111
Reserved
010 0000
Instruction address compare 1 IAC1
010 0001
Instruction address compare 2 IAC2
010 0010
Instruction address compare 3 IAC3
010 0011
Instruction address compare 4 IAC4
010 0100
Data address compare 1 DAC1
010 0101
Data address compare 2 DAC2
010 0110
Data Value Compare 1 (DVC1) (e200z335 only)
010 0111
Data Value Compare 2 (DVC2) (e200z335 only)
010 1000–010 1011
Reserved
010 1100
Debug counter register DBCNT
010 1101
Debug PCFIFO (PCFIFO) read–only
010 1110–010 1111
Reserved
011 0000
Debug status register DBSR
011 0001
Debug control register 0 DBCR0
011 0010
Debug control register 1 DBCR1
011 0011
Debug control register 2 DBCR2
011 0100
Debug control register 3 DBCR3
011 0101
Debug control register 4 DBCR4 (e200z335 only)
011 0110–011 1110
Reserved (do not access)
011 1111
Debug External Resource Control (DBERC0) (e200z335 only)
100 0000–110 1111
Reserved (do not access)
111 0000–111 1001
General purpose register selects [0–9]
111 1010–111 1011
Reserved
111 1100
Nexus2/3–Access–See
111 1101
Reserved
111 1110
Enable_OnCE
1
1
Causes assertion of the
j_en_once_regsel output. Refer to
Section 9.5.5.3, “OnCE Control Register (OCR).”
Table 9-7. OCMD Field Descriptions (continued)
Bits Name
Description