5
3.6 ALARM OUTPUTS (HI, LO, GO)
These three-state outputs are enabled with Digits 4, 5 and 6. S8, S9, and S10
connect HI, LO, and GO to P4-U1, L1 and U2, respectively. The polarity is positive
true (high level corresponds to an alarm condition) when a jumper is installed on
S4-A.
3.7 DATA READY OUTPUT
The output is always valid because the parallel BCD data updates synchronously
with a single clock pulse. A negative true DATA READY signal goes high,
however, for about 0.2 milliseconds when the parallel BCD data is updated.
3.8 INSTRUMENT SELECT INPUTS (P4-U23, L23, U24 AND L24)
These are TTL-compatible inputs with 47 k Ohms pull-up resistors. When the input
logic levels match the instrument address (set by S1), the outputs are enabled.
When the logic levels do not match, they are in high impedance. Refer to Table 3-1.
3.9 HOLD INPUT
When low, this input freezes the outputs and makes the DATA READY low true.
The internal BCD data continues to update. The updated data replaces the
outputs when HOLD goes high.*
* If the HOLD input goes high during transmission, the output update is postponed in
order to prevent erroneous output. Each transmission requires approximately 10
milliseconds.
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