tm1300 NXP Semiconductors, tm1300 Datasheet - Page 101

• Manufacturer Part Number: tm1300
• Description: Tm-1300 Media Processor
• Manufacturer: NXP Semiconductors

Philips Semiconductors
6.6
In this mode, VI receives 8-bit message data over the
VI_DATA[7:0] pins. The message data is written in
packed form (four 8-bit message bytes per 32-bit word)
to SDRAM. Message data capture starts on receipt of a
START event on VI_DATA[8]. Message data is received
until EndOfMessage (EOM) is received on VI_DATA[9]
or the receive buffer is full. Note that the VI_SIZE MMIO
register determines the buffer size, and hence maximum
message length. It should not be changed without a VI
(soft) reset.
Figure 6-17
transfer. The first byte (D0) is sampled on the rising edge
of the VI_CLK clock after a valid START was sampled on
the preceding rising clock edge. The last byte (D7) is
sampled on the rising clock edge where EOM is sampled
asserted.
The message passing mode view of the VI MMIO regis-
ters is shown in
Figure 6-16. VI raw mode major states.
Figure 6-17. VI message passing signal example.
VI_DATA[7:0]
VI_DATA[8]
VI_DATA[9]
MESSAGE-PASSING MODE
VI_CLK
illustrates an example of an 8-byte message
Figure
6-15. The major states are shown
RESET
message
Start of
ACK2
XX
D0
D1
ACTIVE = BUF1
ACTIVE = BUF2
ACTIVE = BUF2
ACTIVE = BUF1
Buffer1
BUF1FULL
Buffer2
BUF2FULL
ACK1
D2
Full
Full
D3
in
operation in raw-capture mode, except that transitions to
another active buffer occur upon receipt of EOM rather
than on buffer full. OVERRUN is raised if the second
buffer receives a complete message before a new buffer
is assigned by the DSPCPU.
OVERFLOW is raised if a buffer is full and no EOM has
been received. If enabled, it causes a DSPCPU interrupt.
Since digital interconnection between devices is reliable,
overflow is indicative of a protocol error between the two
TM1300s involved in the exchange (failure to agree on
message size). Detection of overflow leads to total halt of
capture of this message. Capture resumes in the next
buffer upon receipt of the next START event on
VI_DATA[8]. The OVERFLOW flag is sticky and can only
be cleared by writing a ‘1’ to ACK_OVF.
Highway bandwidth error behavior in message passing
mode is identical to that of raw mode.
PRODUCT SPECIFICATION
Figure
D4
6-18. The operation is almost identical to the
D5
* OVERRUN is a sticky flag. It is set but does not af-
fect operation. It can only be cleared by software, by
writing a ‘1’ to ACK_OVR.
(See text in
raise OVERRUN*
BUF1FULL
BUF2FULL
D6
Section
message
End of
D7
6.5)
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XX
Video In
6-11