peripherals in trimedia interrupts the processor when it has used up the current buffer. Current buffer from which the data is being transmitted is set in the status bit. Intially when transfer is enabled HW will transfer data from buffer 1 and when it
is finished it will raise a buffer 1 empty interrupt and starts transferring data from buffer2. when buffer 2 is finished it will raise buf 2 empty interrupt and will see whether the interrupt for buf 1 is acknowledged or not. if not it will raise an
underrun interrupt. if acknowledged it will transfer data from buffer 1 . the process go on.
HW will interrupt after transferring data from the buffer. if the interrupt for the other buffer is not yet acknowledged it will flag underrun interrupt else start data transfer from the other buffer.
having said this answer to your question:
1.After the last byte of the first first buffer is transferred interrupt is generated. before that the second buffer should be ready.
2. after the last byte is transferred it will generate interrupt.
for more info please refer table 7-5 of page 7-16(explanation for BFR1_EMPTY)
on 11/11/2000 06:53:01 AM
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Subject: [trimedia] VO raw mode question
I have following questions regarding raw mode of VO peripheral.
1. I am using VO peripheral of TM1300 in raw mode. I am setting SIZE1 & SIZE2 = 256. Also, BFR1_EMPTY, BFR2_EMPTY, HBE & URUN
interrupts are enables.
Since VO peripheral has an internal data buffer of 64 bytes, it has to raise a request on highway for next 64 bytes while transmitting
current 64 bytes from internal data buffer.
When VO is transmitting last 64 bytes of BUFFER1 (current active buffer), it has to raise a request for next 64 bytes, which
happen to be in BUFFER2 (current empty buffer). Now, if VO generates an interrupt after transmitting last byte of BUFFER1,
first 64 bytes from BUFFER2 (current empty buffer) are actually being read before BFR1_EMPTY interrupt occurs.
Is this true ?
If not, when does VO peripheral actually generates an interrupt ?
2. After enabling VO peripheral, when is the first interrupt (BFR1_EMPTY) generated ?
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