Epson ARM.POWERED ARM720T - Manual (Page 172)

9: Debugging Your System
9-40 EPSON ARM720T CORE CPU MANUAL
9.24.1 Disabling interrupts
IRQs and FIQs are disabled under the following conditions:
• during debugging (DBGACK HIGH)
• when the INTDIS bit is set.
The core interrupt enable signal, IFEN, is driven as shown in Table 9-10.
9.24.2 Forcing DBGRQ
Figure 9-17 on page 9-42 shows that the value stored in bit 1 of the Debug Control Register is
synchronized and then ORed with the external DBGRQ before being applied to the processor.
The output of this OR gate is the signal DBGRQI which is brought out externally from the
macrocell.
The synchronization between Debug Control Register bit 1 and DBGRQI assists in
multiprocessor environments. The synchronization latch only opens when the TAP controller
state machine is in the RUN-TEST-IDLE state. This enables an enter-debug condition to be
set up in all the processors in the system while they are still running. When the condition is
set up in all the processors, it can be applied to them simultaneously by entering the
RUN-TEST-IDLE state.
9.24.3 Forcing DBGACK
Figure 9-17 on page 9-42 shows that the value of the internal signal DBGACKI from the core
is ORed with the value held in bit 0 of the Debug Control Register, to generate the external
value of DBGACK seen at the periphery of the ARM720T core. This enables the debug system
to signal to the rest of the system that the core is still being debugged even when system-speed
accesses are being performed (when the internal DBGACK signal from the core is LOW).
Table 9-10 Interrupt signal control
DBGACK INTDIS IFEN Interrupts
0 0 1 Permitted
1 x 0 Inhibited
x 1 0 Inhibited