Freescale-semiconductor StarCore SC140 Manual do Utilizador descarregar pdf (Página 117)

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Overview of the Combined JTAG and EOnCE Interface

SC140 DSP Core Reference Manual 4-7

Figure 4-3. Cascading Multiple EOnCE Modules

4.2.5 DEBUG_REQUEST and ENABLE_EONCE Commands

After the CHOOSE_EONCE instruction completes, DEBUG_REQUEST and ENABLE_EONCE

instructions can be executed. More than one such instruction can execute, and other instructions can be

placed between them and also between them and the CHOOSE_EONCE instruction. The EOnCE modules

selected in the CHOOSE_EONCE instruction remain selected until the next CHOOSE_EONCE

instruction. The DEBUG_REQUEST or ENABLE_EONCE instruction is shifted in during the Shift-IR

state, as are all JTAG instructions.

4.2.6 Reading/Writing EOnCE Registers Through JTAG

An external host can read or write almost every EOnCE register through the JTAG interface, using the

following steps (see Figure 4-4):

1. Execute the CHOOSE_EONCE command in the JTAG.

2. Send the data showing which EOnCE is chosen. This command enables the JTAG to manage

multiple EOnCE modules in a device.

3. Execute the ENABLE_EONCE command in the JTAG.

4. Write the EOnCE command into the EOnCE Command register (ECR).

That is, the host enters the JTAG TAP state machine into the shift-dr state and then gives the required

command on the

TDI input signal. After the command is shifted in, the JTAG TAP state machine

must enter the update-dr state. The data shifted via the

TDI is sampled into the ECR. For example, if

the command written into the ECR is “Write EDCA0_CTRL,” then the host must again enter the

JTAG into shift-dr and shift the required data, which is to be written into the EDCA0_CTRL, via

TDI. If the command is “read some register,” then the DR chain must be passed again and the

contents of the register are shifted out through the

TDO output.

Choose

TDI

Controls

JTAG

CORE 1

EOnCE

Choose

CORE n

EOnCE

SC140

to TDO mux

1 2 ... 112 113 114 115 116 117 118 119 120 121 122 ... 759 760

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