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HP 27130B
SID
NO.
o
I 0
SID
MNEMONIC
RTSA-
(OUTPUT)
DTRB-
(OUTPUT)
MUX CARD
MNEMONIC
Table 3-6. SIO Special Functions
FUNCTION
Active LOW.
When asserted, the
RS-232-C/RS-423-A single-ended
drivers are enabled.
Otherwise,
the transmission lines (SDs) of
the single-ended drivers are
held in a MARK condition (negative
vol tage).
To assert the EN_SED signal, a 1 must
be written into bit 1 of SIO
0 channel
A, register 5.
On power up (reset), EN_SED is
unasserted, i.e., the transmission
lines (SDs) of the Single-ended
drivers are in a MARK condition.
Active HIGH.
When asserted, the
RS-422-A differential drivers are
enabled.
Otherwise, the
transmission lines (SD(A), SD(B»
of the differential drivers are
held in a high impedance state.
To assert the EN_DD Signal. a 0
must be written into bit 7 of SIO
0
channel B, register 5.
On power up (reset), EN_DD is
asserted. i.e., the differential
drivers are enabled.
3-14
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