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Command, Status, and Control Registers

12.4.5.4 Data/Address Select (DAT)—Bit 0

The data/address select (DAT) bit determines which bus is selected by the second breakpoint unit. When DAT is set, the second breakpoint unit examines the core global data bus (CGDB). When DAT is cleared, the program address bus (PAB) is examined.

12.4.6 OnCE Status Register (OSR)

The OnCE status register (OSR) is shown in Figure 12-9. By observing the values of the 5 status bits in the OSR, the user can determine if the core has halted, what caused it to halt, or why the core has not halted in response to a debug request. The user can see the OSR value when shifting in a new OnCE command (writing to the OCMDR), allowing for efficient status polling. The OSR (and all other OnCE registers) are inaccessible in stop mode.

OSR

7

6

5

4

3

2

1

0

OnCE Status

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Register

*

*

*

OS1

OS0

TO

HBO

SBO

OnCE Reset = $00

 

 

 

 

 

 

 

 

Read-Only

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

AA0108

Figure 12-9. OSR Programming Model

12.4.6.1 Reserved OSR Bits—Bits 7–5

Bits 7–5 of the OSR are reserved for future expansion and are read as zero during DSP read operations.

12.4.6.2 OnCE Core Status (OS[1:0])—Bits 4–3

The OnCE core status (OS[1:0]) bits describe the operating status of the DSP core. It is recommended that the user read JTAG IR for OS[1:0] information, because OSR is unreadable in stop mode. Table 12-13 summarizes the OS[1:0] descriptions. On transitions from 00 to 11 and from 11 to 00, there is a small chance that intermediate states (01 or 10) may be captured.

 

 

Table 12-13. DSP Core Status Bit Description

 

 

 

 

OS[1:0]

Instruction

 

Description

 

 

 

 

 

 

 

 

00

Normal

 

DSP core executing instructions or in reset

 

 

 

 

01

STOP/WAIT

 

DSP core in stop or wait mode

 

 

 

 

10

Busy

 

DSP is performing external or peripheral access (wait states)

 

 

 

 

11

Debug

 

DSP core halted and in debug mode

 

 

 

 

NOTE:

The OS bits are also captured by the JTAG instruction register (IR). See

Section 12.10.3, “Loading the JTAG Instruction Register,” for details.

 

OnCE™ Module

12-21

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