Table 5. Example Semaphore Procurement Sequence
Function
D0 - D15 Left
No Action
1
D0 - D15 Right
1
Status
Semaphore free
Left Port Writes ’0’ to Semaphore
0
1
Left Port has semaphore token
Right Port Writes ’0’ to Semaphore
0
1
No change. Right side has no write
access to semaphore
Left Port Writes ’1’ to Semaphore
1
0
Right port obtains semaphore token
Left Port Writes ’0’ to Semaphore
1
0
No change. Left port has no write
access to semaphore
Right Port Writes ’1’ to Semaphore
0
1
Left port obtains semaphore token
Left Port Writes ’1’ to Semaphore
1
1
Semaphore free
Right Port Writes ’0’ to Semaphore
1
0
Right port has semaphore token
Right Port Writes ’1’ to Semaphore
1
1
Semaphore free
Left Port Writes ’0’ to Semaphore
0
1
Left Port has semaphore token
Left Port Writes ’1’ to Semaphore
1
1
Semaphore free
Note: 1. This table denotes a sequence of events for only one of the 8 semaphores on the M67025E.
Figure 1. Semaphore Logic
10 M67025E
4146N–AERO–04/07