Rainbow Electronics MAX781 - Manual (Page 21)

Interfacing the MAX781 to an
IBM Compatible PC
Figure 1 shows the MAX781 typical operating circuit.
On power-up, with 4.8V < BATT < 18V and CE = SCLK
= DIN = 0V, the MAX781 is in low-power mode. 3OUT
outputs +3.3V linear regulated from BATT, and REF
outputs +2.5V. INT should output a 3.3V logic high.
Neither DHI nor DLO should be switching. Serial data
must be sent to the MAX781 in order to change modes.
The parallel printer interface on a personal computer
can be used to send serial control data to the MAX781.
Listing 3 shows a simple Microsoft Quick Basic pro-
gram for communicating with the MAX781 over the
LPT1 parallel interface port.
MAX781
PDA/Hand-Held Computer Power Controller
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