Freescale Semiconductor StarCore SC140 - Manual (Page 158)

4-48 SC140 DSP Core Reference Manual
EOnCE Controller Registers
4.7.7 Core Command Register (CORE_CMD)
The CORE_CMD register is used to execute instructions in the core while in debug state. The external host
writes the instruction into the CORE_CMD register as described in
Section 4.2.6, “Reading/Writing
EOnCE Registers Through JTAG.” The EOnCE commands written into the ECR must be Write
CORE_CMD and GO. After writing the instruction into the CORE_CMD register, the core executes it
without leaving debug state. If the EX bit in ECR is also set, debug state is exited after the instruction is
performed.
The format of the injected command is shown in Figure 4-19 below.
Figure 4-19. Injected Instruction Format
The length control bits are described in Table 4-17, below:
The two prefix bits allow the instruction to use the high bank of registers. Bits 15 and 14 in the second and
third words encode the grouping/word partition used by the core for execution set parsing. In the case of a
single instruction, they do not need to be part of the CORE_CMD word. For further details, see
Appendix A, “SC140 DSP Core Instruction Set.”
In general, core commands should not perform illegal operations. In case a core command generated an
exception (such as an illegal exception), the exception will be serviced only after the core exits debug state.
Table 4-17. Length Control Bits
Length Control Bits Description
0 0 Not supported
0 1 One word instruction
1 0 Two word instruction
1 1 Three word instruction
ImmB
14 bits
bits [0:13] ImmA
14 bits
bits [0:13] Opcode
16 bits
bits [0:15] Ext.
Prefix
2 bits Length
Control
2 bits
{Prefix1[5], Prefix1[7]}
Prefix1 Prefix2 Opcode ImmA ImmB
[15:0] [15:0] [15:0] [15:0] [15:0]
Bit 47 34 33 20 19 4 3 2 1 0
Instruction Bus (IB)
CORE_CMD