HP 64783A, User Manual

Page: 677 / 816

When a software breakpoint instruction is executed, the processor initiates a
breakpoint-acknowledge cycle. This cycle signals the start of an entry into the
monitor. From this point on, stacking and the vector fetch procede the same as for
a break entry. Unlike the interrupt-acknowledge cycle, the
breakpoint-acknowledge cycle is shown to the target system.
tsto any
tg stat=11xxxxxxxx1x000xy
t
r 8
Line addr,H 68040 Mnemonic
----- -------- ------------------------------------------
-4 00000008 $484F0000 sprog long read <-bkpt fetch
-3 0000000c $000BADAD sprog long read
-2 00000010 $000BADAD sprog long read
-1 00000014 $00000000 sprog long read
0 00000000 $41------ bkpt ack (buserror) <-acknowledge
1 000000ee $----0010 sdata word write <-stack format
2 000000ea $----0000 sdata word write <-stack PC high
3 000000ec $0008---- sdata word write <-stack PC low
4 00000010 $00000690 sdata long read <-vector fetch
5 000000e8 $2700---- sdata word write <-stack SR
6 00000690 $11FC0004 mon sprog long read <-monitor
7 00000694 $01186000 mon sprog long read
The only unique portion of a breakpoint entry is the breakpoint-acknowledge cycle
so any problems that you see will probably be related to this cycle. Because the
emulator internally responds to this cycle, it is not necessary for the target system to
respond to it. If the target system does respond to this cycle with any wait states,
the emulator may become out of sync with the target system because the emulator
terminates this cycle immediately. If this were to cause a problem, it would show
up on the cycle immediately following the breakpoint-acknowledge cycle.
Chapter 18: Connecting the Emulator to a Target System
Installing Emulator Features
647