Chapter 18 Version 1 ColdFire Debug (CF1_DEBUG)

CPU clock/2 is used

Debug

 

 

 

Halt

 

Return to Halt via

as the BDM clock

 

ENBDM=1

 

BACKGROUND command,

 

 

 

(POR or BDFR=1) with BKGD=0 or

 

 

BDM GO

HALT instruction, or

 

 

BDM breakpoint trigger

BDFR and BFHBR= 1

CLKSW=1

 

command

 

 

 

 

Any

 

 

 

Normal

 

 

 

 

Operation

 

State

 

 

 

 

 

 

 

ENBDM=1

Debug is enabled

 

 

 

 

 

 

 

 

 

CPU clocks continue

POR with BKGD=1 or

 

 

 

 

during STOP modes

 

 

clear ENBDM

 

BDFR, BFHBR, and BKGD=1 or CLKSW=0

 

 

 

via BDM

 

 

BDFR=1 and BFHBR=0 or

 

 

 

 

 

 

 

Set

 

any other reset

 

 

 

 

 

 

Normal

 

ENBDM

 

 

 

Operation

 

 

 

Debug not enabled ENBDM=0

 

 

 

BDM & CPU clocks are not enabled in STOP modes

Figure 18-2. Debug Modes State Transition Diagram

Figure 18-2contains a simplified view of the V1 ColdFire debug mode states. The XCSR[CLKSW] bit controls the BDC clock source. When CLKSW is set, the BDC serial clock is half the CPU clock. When CLKSW is cleared, the BDC serial clock is ICSLCLK. This signal is supplied from the on-chip 10 MHz bus clock/20 MHz CPU clock frequency locked loop. Normally, ICSLCLK should be used when the device in in any of the following clock modes: FBE, FEI, FBI, and FEE. The FLL clocks are not available when the device is in FBELP and FBILP modes. In these cases, ICSOUT should be used.

The ENBDM bit determines if the device can be placed in halt mode, if the core and BDC serial clocks continue to run in STOP modes, and if the regulator can be placed into standby mode. Again, if booting to halt mode, XCSR[ENBDM, CLKSW] are automatically set.

If ENBDM is cleared, the ColdFire core treats the HALT instruction as an illegal instruction and generates a reset (if CPUCR[IRD] is cleared) or an exception (if CPUCR[IRD] is set) if execution is attempted.

If XCSR[ENBDM] is set, the device can be restarted from STOP/WAIT via the BDM interface.

18.2External Signal Descriptions

Table 18-3describes the debug module’s 1-pin external signal. A standard 6-pin debug connector is shown in Section 18.4.4, “Freescale-Recommended BDM Pinout”.

 

 

Table 18-3. Debug Module Signals

 

 

 

 

 

 

 

 

Signal

Description

 

 

 

 

 

 

 

Background Debug

Single-wire background debug interface pin. The primary function of this pin is for bidirectional serial

 

 

(BKGD)

communication of background debug mode commands and data. During reset, this pin selects

 

 

 

 

between starting in active background (halt) mode or starting the application program. This pin also

 

 

 

requests a timed sync response pulse to allow a host development tool to determine the correct clock

 

 

 

frequency for background debug serial communications.

 

 

 

 

 

 

 

 

 

MCF51QE128 MCU Series Reference Manual, Rev. 3

 

 

 

 

 

 

 

Freescale Semiconductor

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Freescale Semiconductor MCF51QE128RM manual External Signal Descriptions, Bdm Go, Debug Module Signals Description