Communications Block; Serial Data; Parallel Data - Sony DVP S530D Training Manual

Communications Block

Both serial and parallel bus structures are used in the same unit of today's
DVD players. The serial data bus is a simple way to provide communica-
tions between ICs. On one line, data is transmitted one bit after another
to the next IC in 8, 16, 20, 24 or 32 bit groups. On another line, corre-
sponding clock pulses accompany the bits of data. One clock pulse iden-
tifies each bit of data - this is why this line is also called a bit clock. There-
fore, it takes 8, 16, 20, 24 or 32 clock pulses to receive a group of data in
a serial bus.
A parallel data bus is used when large amounts of data need to be trans-
mitted in a shorter time frame. In the parallel bus, multiple data lines are
used along with a clock line. When a single clock pulse is sent, the 8, 16,
20, 24 or 32 lines each simultaneously transmit a bit of data to the receiv-
ing IC. (Only 16 data lines are used here.) Therefore, it takes only one
clock pulse to receive a group of data in a parallel bus.
The parallel bus is used in processing video information (IC401) and in
the disc playback servo (IC701) where large amounts of data must be
handled quickly.

Serial Data

The serial data bus connects several ICs and consists of two or three
lines. Serial data is transmitted from one IC to another on a unidirectional
line (arrows shown in one direction). This data is accompanied by a clock
signal for a total of two lines in a unidirectional serial communication.
The interface control IC201 and System Control IC202 communicate
bidirectionally (arrows shown in two directions). Three lines are neces-
sary when bi-directional transmissions are called. There is a data line for
each direction. The additional clock signal makes a total of three lines for
a bi-directional serial bus. The clock signal usually comes from the con-
trolling micro, which in this case is System Control IC202.
System Control IC202 communications with Interface IC201, EEProm
IC201 and DSP IC501 are bi-directional. System Control communica-
tions to the Digital to Analog Converters (DAC) IC902, IC905-7 are unidi-
rectional.
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Parallel Data

The parallel data bus is much more complicated than the serial bus. It
consists of address lines, data lines and a clock line. Just before data is
transmitted from one IC to another, a location is designated using ad-
dress lines. Then clock pulses are sent from the master IC202 to transfer
the data into the receiving IC.
When communications are bi-directional on the parallel bus, an additional
line identified as write enable (WE) and/or read enable (RE) is used. These
lines determine the direction of the data to or from the master IC. When
there is no WE or RE line, the bi-directional data communication is pre-
established first as read-data from the master micro. Write-data occurs
afterwards.