MPC563XM Reference Manual, Rev. 1
668
Freescale Semiconductor
Preliminary—Subject to Change Without Notice
As part of the coherency mechanism, reading EMIOSA[n] disables transfers from B2 to B1. These
transfers are disabled until the next read of the EMIOSB[n] register. Reading the EMIOSB[n] register
re-enables transfers from B2 to B1, to take effect at the next transfer event, as described above.
1
In order to have coherent data in continuous mode of operation the following steps should be performed,
assuming FLAG is initially cleared:
1. Wait for FLAG assertion;
2. Read EMIOSA[n] register;
3. Read EMIOSB[n] register;
4. Clear FLAG bit;
5. Return to step 1.
Accumulation cycles may be lost if the read is not performed in a timely manner. Whenever Overrun bit
is asserted it means that one or more cycles have been lost.
Triggering of the counter clock (input event) is done by a rising or falling edge or both edges on the input
pin. The polarity of the triggering edge is selected by the EDSEL and EDPOL bits in EMIOSC[n] register.
For continuos operation mode (MODE[6] cleared, MODE[0:6]=0001000), the counter is cleared on the
next input event after a FLAG generation and continues to operate as described above.
For single shot operation (MODE[6] set, MODE[0:6]=0001001), the counter is not cleared or incremented
after a FLAG generation, until a new writing operation to register A is performed.
show how the Unified Channel can be used for continuos and single shot
pulse/edge accumulation mode.
1.
If B1 was not updated due to B2 to B1 transfer being disabled after reading register EMIOSA[n], further EMIOSA[n] and
EMIOSB[n] reads will not return coherent data until a new bus capture is triggered to registers A2 and B2. This capture
event is indicated by the channel FLAG being asserted. If enabled, the FLAG also generates an interrupt.