X-10 Technical Specification
X-10 communicates between transmitters
and receivers by sending and receiving signals over the power line wiring.
These signals involve short RF bursts which represent digital information.
X-10 transmissions are synchronized
to the zero crossing point of the AC power line. The goal should be to
transmit as close to the zero crossing point as possible, but certainly
within 200 microseconds of the zero crossing point. The PL513 and TW523
provide a 60 Hz square wave with a maximum delay of 100 µsec
from the zero crossing point of the AC power line. The maximum delay between
signal envelope input and 120 kHz output bursts is 50 µsec. Therefore,
it should be arranged that outputs to the PL513 and TW523 be within 50
µs of this 60 Hz zero crossing reference square wave.
A complete code transmission encompasses
eleven cycles of the power line. The first two cycles represent a Start
Code. The next four cycles represent the House Code and the last five cycles
represent either the Number Code (1 thru 16) or a Function Code (On, Off,
etc.). This complete block, (Start Code, House Code, Key Code) should always
be transmitted in groups of 2 with 3 power line cycles between each group
of 2 codes. Bright and dim are exceptions to this rule and should be transmitted
continuously (at least twice) with no gaps between codes. See Figure 2..
Within each block of data, each
four or five bit code should be transmitted in true compliment form on
alternate half cycles of the power line. I.E. if a 1 millisecond burst
of signal is transmitted on one half cycle (binary 1) then no signal should
be transmitted on the next cycle, (binary 0). See Figure 3.
A Binary 1 is represented by a
1 millisecond burst of 120 kHz at the zero crossing point, and a Binary
0 by the absence of 120 kHz. The PL513 and TW523 modulate their inputs
(from the O.E.M.) with 120 kHz, therefore only the 1 ms "envelope" need
be applied to their inputs. These 1 millisecond bursts should equally be
transmitted three times to coincide with the zero crossing point of all
three phases in a three phase distribution system. Figure 1 shows the timing
relationship of these bursts relative to zero crossing.
The Tables in Figure 4 show the binary
codes to be transmitted for each House Code and Key Code. The Start Code
is always 1110 which is a unique code and is the only code which does not
follow the true complimentary relationship on alternate half cycles.
 Hail Request is transmitted to see
if there are any X-10 transmitters within listening range. This allows
the O.E.M. to assign a different Housecode if a "Hail Acknowledge" is received.
 In a Pre-Set Dim instruction, the
D8 bit represents the Most Significant Bit of the level and H1, H2, H4
and H8 bits represent the Least Significant Bits.
 The Extended Data code is followed
by 8 bit bytes which can represent Analog Data (after A to D conversion).
There should be no gaps between the Extended Data code and the actual data,
and no gaps between data bytes. The first 8 bit byte can be used to say
how many bytes of data will follow. If gaps are left between data bytes,
these codes could be received by X-10 modules causing erroneous operation.
Extended Code is similar to Extended
Data: 8 Bit bytes which follow Extended Code (with no gaps) can
represent additional codes. This allows the designer to expand beyond the
256 codes presently available.
X-10 Receiver Modules require a "silence" of at least 3 power
cycles between each pair of 11 bit code transmissions (no gaps between
each pair). The one exception to this rule is bright and dim codes. These
are transmitted continuously with no gaps between each 11 bit dim code
or 11 bit bright code. A 3 cycle gap is necessary between different codes,
i.e. between bright and dim, or 1 and dim, or on and bright, etc.
The TW523 Two-Way Power Line Interface cannot receive Extended Code or
Extended Data because these codes have no gaps between them. The TW523
can only receive standard "pairs" of 11 bit X-10 codes with 3 power line
cycle gaps between each pair.
The TW523 can receive dim and bright codes but the output will represent
the first dim or bright code received, followed by every third code received.
i.e. the output from the TW523 will not be a continuous stream of dim and
bright codes like the codes which are transmitted.
A Square wave representing zero crossing
detect is provided by the PL513/TW523 and is within 100 µs of
the zero crossing point of the AC power line. The output signal envelope
from the O.E.M. should be within 50 µs of this zero crossing
detect. The signal envelope should be 1 ms (-50µs +100µs).
See Figure 5. .
60 Hz reference output (from the PL513/TW523)
Transmissions are to be synchronized to the zero crossing point of the
AC power line and should be as close to true zero crossing as possible.
The PL513 and TW523 are designed to be interfaced to other microprocessor
circuitry which outputs X-10 codes synchronized to the zero crossing point
of the AC power line. It is therefore necessary to provide a zero crossing
reference for the O.E.M. microprocessor.
It is likely that this microprocessor
will have its own "isolated" power supply. It is necessary to maintain
this isolation, therefore the trigger circuit normally used in X-10 POWERHOUSE
controllers is not desirable as this would reference the O.E.M.
power supply to the AC power line. It is also not desirable to take
the trigger from the secondary side of the power supply transformer as
some phase shift is likely to occur. It is therefore necessary to provide
an opto-coupled 60 Hz reference.
An opto-coupled 60 Hz square wave is
provided at the output of the PL513 and TW523. X-10 codes generated by
the O.E.M. product are to be synchronized to this zero crossing reference.
The X-10 code envelope generated by the O.E.M. is applied to the PL513
or TW523 which modulates the envelope with 120 kHz and capacitively couples
it to the AC power line.
Signal Output (from the TW523)
The "X-10 received" output from the TW523
coincides with the second half of each X-10 transmission. This output is
the envelope of the bursts of 120 kHz received. Only the envelope corresponding
to the first burst of each group of 3 bursts is available at the output
of the TW523.
See Figures 6, 7 and 8.