Interface Circuit; (2-L) Sync Interface Circuit - NEC MultiSync 4FGe Service Manual

2. Interface Circuit

2-1. Sync Interface Circuit
(a) The outputs of this circuit are the positive H Sync and V Sync.
The following three signals are designed as input signals.
(i)
SEPARATE SYNC
(ii) COMPOSITE SYNC
(iii) SYNC ON GREEN
S Y N C O N
H SEPARATE -
H V COMPOSITE
V SEPARATE -
(b) The outputs of the distinction circuit are as follows:
These outputs are supplied to IC851 (CPU) on the main PWB.
H SYNC signals's polarity (CN-A PIN 1)
l
V SYNC signal's polarity (CN-A PIN 2)
l
. V SYNC STATE (EXISTENCE)(CN-A PIN 3)
NOTE:
H
POSITIVE/NEGATIVE polarity
POSITIVE/NEGATIVE polarity
NEGATIVE polarity
G
SHAPER
(Fig 2-l-l) BLOCK-DIAGRAM of the SYNC INTERFACE CIRCUIT
L Low level of TTL
High level of TTL
L: POSITIVE POLARITY
H: NEGATIVE POLARITY
L: POSITIVE POLARITY
H: NEGATIVE POLARITY
L: NONE
H: AVAILABLE
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