Hitachi RAS-25QH1 Technische Information Seite 151

3.2 Interface circuit between outdoor microcomputers
Circuits for indoor unit 1 and 2 (circuit A) | Circuits for indoor unit 3 (circuit B)
Center-to-center J .
reception
Center-to-center
Outd
® transmission
utdoor
microcomputer A
Outdoor
microcomputer B
. Center-to-center
reception
Center-to-center
transmission
> Caution: The OV levels of circuits A and B are different
Fig. 3-5
e@ The interface circuit between the outdoor microcomputers refers to that between microcomputer A,
which communicates with indoor unit 1 and 2, and microcomputer B, which communicates with indoor unit.
It consists of PQ201A, PQ201B and their peripheral circuits.
e@ The interface circuit between the outdoor microcomputers uses A as the main microcomputer and B as
the sub microcomputer.
e@ The main and sub-microcomputers communicate with each other by transmitting the leader of approx.
100 ms and a 4-frame signal with each frame consisting of a start bit, 8-bit data and a stop bit alternately.
@ The signal output from pin © of the main microcomputer (computer A) is supplied via PQ201A to pin
(® of the sub microcomputer (microcomputer B).
When the sub microcomputer receives the signal from the main microcomputer, it outputs the signal from
pin © and supplies it via PQ201B to pin (0 of the main microcomputer.
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