OBCB_StartA c [D>=19]
Start OBCB c in Phase A
Start counting pulses on counting input c using the OnBoard Counter B (Firmware) counter. Counting will start when the OBCB time base is in phase A. If the time base is in phase A when the instruction is executed, counting starts at once. If it is in phase B, counting will start when it next enters phase A.
Arm Difference
In ARM, counting only occurs during phase A and does NOT occur during phase B. This means your SPLat application has plenty of time to “read & clear” the count during phase B so when phase A next occurs counting will automatically start from zero.
In legacy boards the SPLat application must call OBCB_StopB to ensure counting stops. This however means it must repeat the process of starting again. If OBCB_StopB is not called then counting will occur during both phase A and B.
+ The channel argument will be jndexed when executed inside a MultiTrack task and will be indexed if the instruction is preceded by the IasJ: precode.
Dialect exclusions: Not available in dialects before 19.
| Note: At time of writing there is no simulation of the OBCA in SPLat/PC |
See also: OBCB_GoIfA, OBCB_GoIfB, OBCB_Start, OBCB_Stop, OBCB_StopB, OBCB_fRead, OBCB_fRdClr
Alternative counter mechanisms: OnBoard Counter A, OnBoard Quadrature Counter