int e l + 10 TO + 15 VOLTS 10K + 5 + 5 2N4403 7407 10K 4.7K + 5 4.7K Q R B A Q R B A (PIN 1) Vpp 15K Ω 15K PSEN RD 7407 OE (PIN 20) Rx/C 5uF + 5 Rx/C 5uF + 5 74LS08 Cx Cx TO ADDRESS DECODE LOGIC (ACTIVE LOW) 7407 CE (PIN 18) Ѕ 74221 Ѕ 74221 10K + 5 2 8 1 6 A 74LS08 7407 WE (PIN 21) P1.4 PROGRAM PULSE WIDTH Figure 5. 2816A Circuit with Push Button Erase (Basic-52 should be „idle“ in the command mode when the Erase Button is pushed.) +5 4.7K 4.7K TO RXD ON BASIC-52 DEVICE +5 SERIAL OUTPUT 2N2222 OR EQUIV. SERIAL OUTPUT TO RXD ON BASIC-52 DEVICE 1N914 OR EQUIV.
1/4 1489 +5 4.7K +12 -12 TO TXD ON BASIC-52 DEVICE SERIAL OUTPUT TO TXD ON BASIC-52 DEVICE SERIAL OUTPUT 4.7K 1/4 1488 1.8K 10uF 15V Figure 6A. Figure 6B. TWO TRANSISTORS TO IMPLEMENT RS-232. THE “NEGATIVE” SUPPLY FOR THE SERIAL OUTPUT LINE IS TAKEN FROM THE SERIAL INPUT LINE. NO ±12 VOLT SUPPLY IS REQUIRED. USING THE STANDARD 1489 AND1488 LINE RECEIVERS AND DRIVERS. ±12 VOLT IS NEEDED WITH THIS IMPLEMENTATION. - 144 -