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CDP1871ACDX датащи(PDF) 7 Page - Intersil Corporation |
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CDP1871ACDX датащи(HTML) 7 Page - Intersil Corporation |
7 / 10 page 4-72 Operation The CDP1871A is made up of two major sections: the counter/scan-selection logic and the control logic (Figure 2). The counter and scan-selection logic scans the keyboard array using the drive lines (D1-D11) and the sense lines (S1- S8). The outputs of the internal 5-stage scancounter are conditionally encoded by the ALPHA, SHIFT, and CONTROL inputs (Table 1, Table 3) and are used to drive the D1-D11 output lines high one at a time. Each D1-D11 output may drive up to eight keys, which are sampled by the sense line inputs (S1-S8). The S1-S8 inputs are enabled by the internal 3-stage scancounter. The control logic interfaces with the CDP1800-series I/O and timing signals to establish timing and status conditions for the CDP1871A. The TPB input clocks the scancounters and is also used to reset the Data Available output (DA). When a valid keydown condition is detected on a sense line, the control logic inhib- its the clock to the scancounters on the next low-to-high tran- sition of TPB and the DA output is set low. The scancounter outputs (C1 - C8) represent the ASCII and HEX key codes and are used to drive the BUS 0 - BUS 7 outputs, which interface directly to the CDP1800-Series data bus. The BUS 0 - BUS 7 outputs, which are normally three-stated, are enabled by decoding the CS inputs during a CPU input instruction (Table 2). The low-to-high transition of TPB during the input instruction resets the DA output high. Once the DA output has been reset, it cannot go low again until the present key is released and a new keydown condition is detected. (This prevents unwanted repeated keycode out- puts which may be caused by fast software routines). After the depressed key is released and the debounce delay (determined by RX, CX) has occurred, the scan clock inhibit is removed, allowing the scancounters to advance on the fol- lowing high-to-low transitions of TPB. This provides an N-key lockout feature, which prevents the entry of erroneous codes when two or more keys are pressed simultaneously. The first key pressed in the scanning order is recognized, while all other keys pressed are ignored until the first key is released TABLE 4. HEXIDECIMAL VALUES OF ASCII CHARACTERS BITS MSD b7 00001111 b6 00110011 b5 01010101 b4 b3 b2 b1 HEX 01234567 LSD 0000 0 NUL DLE SP 0 @ P \ p 0001 1 SOH DC1 ! 1 A Q a q 0010 2 STX DC2 “ 2 B R b r 0011 3 ETX DC3 # 3 C S c s 0100 4 EOT DC4 $ 4 D T d t 0101 5 ENQ NAK % 5 E U e u 0110 6 ACK SYN & 6 F V f v 0111 7 BEL ETB / 7 G W g w 1000 8 BS CAN ( 8 H X h x 1001 9 HT EM ) 9 I Y i y 1010 A LF SUB * : J Z j z 1011 B VT ESC + ; K [ k { 1100 C FF FS , < L \ l | | 1101 D CR GS - = M ] m } 1110 E SO RS . > N ↑ n~ 1111 F SI US / ? O - o DEL CDP1871A, CDP1871AC |
Аналогичный номер детали - CDP1871ACDX |
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Аналогичное описание - CDP1871ACDX |
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