Once Registers; Once Command Register (Ocmr; Once Command Register - Motorola Freescale Semiconductor M-Core MMC2001 Reference Manual

C.10 OnCE Registers
C.10.1 OnCE Command Register (OCMR)
The OnCE command register (OCMR) is an 8-bit shift register that receives its serial
data from the TDI pin. This register corresponds to the JTAG IR, and is loaded when
the update-IR TAP controller state is entered.
OCMR — OnCE Command Register
BIT 7
R/W GO
R/W — Read/Write Command
The R/W bit specifies the direction of data transfer.
0 = Write the data associated with the command into the register specified by
the RS field.
1 = Read the data contained in the register specified by the RS field.
GO — Go Command
If the GO bit is set, the chip executes the instruction that resides in the IR register in
the CPUSCR. To execute the instruction, the processor leaves debug mode, executes
the instruction, and if the EX bit is cleared, returns to debug mode immediately after
executing the instruction. The processor resumes normal operation if the EX bit is set.
The GO command is executed only if the operation is a read/write to either CPUSCR
or "No register selected". Otherwise, the GO bit is ignored. The processor leaves
debug mode after the TAP controller update-DR state is entered.
0 = Inactive (no action taken)
1 = Execute instruction in IR
EX — Exit Command
If the EX bit is set, the processor leaves debug mode and resumes normal operation
until another debug request is generated. The exit command is executed only if the go
command is issued, and the operation is a read/write to CPUSCR or read/write to "No
register selected". Otherwise the EX bit is ignored. The processor exits debug mode
after the TAP controller update-DR state is entered.
0 = Remain in debug mode
1 = Leave debug mode
RS — Register Select
The register select bits define the source or destination register for the read or write
operation, respectively. Table C-20 indicates the OnCE register addresses.
MOTOROLA
C-46
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6 5 4
EX
Figure C-46 OnCE Command Register
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3 2 1
RS
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BIT 0
MMC2001