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поискавой системы для электроныых деталей |
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поискавой системы для электроныых деталей |
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LM8322 датащи(PDF) 14 Page - National Semiconductor (TI) |
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LM8322 датащи(HTML) 14 Page - National Semiconductor (TI) |
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14 / 42 page  12.0 Keypad Interface 12.1 EVENT CODE ASSIGNMENT After power-on reset and host initialization, the LM8322 starts scanning the keypad. It stays active for a default time of about 500 ms after the last key is released, after which it enters Halt mode to minimize power consumption (typically <5 µA stand- by current). Table 5 lists the codes assigned to the matrix positions en- coded by the hardware. Key-press events are assigned the codes listed in Table 5 , but with the MSB set. When a key is released, the MSB of the code is clear. TABLE 5. Keypad Matrix Code Assignments KP-Y0 KP-Y1 KP-Y2 KP-Y3 KP-Y4 KP-Y5 KP-Y6 KP-Y7 KP-Y8 KP-Y9 KP-Y10 KP-Y11 SF Keys KP-X0 0x01 0x02 0x03 0x04 0x05 0x06 0x07 0x08 0x09 0x0A 0x0B 0x0C 0x0F KP-X1 0x11 0x12 0x13 0x14 0x15 0x16 0x17 0x18 0x19 0x1A 0x1B 0x1C 0x1F KP-X2 0x21 0x22 0x23 0x24 0x25 0x26 0x27 0x28 0x29 0x2A 0x2B 0x2C 0x2F KP-X3 0x31 0x32 0x33 0x34 0x35 0x36 0x37 0x38 0x39 0x3A 0x3B 0x3C 0x3F KP-X4 0x41 0x42 0x43 0x44 0x45 0x46 0x47 0x48 0x49 0x4A 0x4B 0x4C 0x4F KP-X5 0x51 0x52 0x53 0x54 0x55 0x56 0x57 0x58 0x59 0x5A 0x5B 0x5C 0x5F KP-X6 0x61 0x62 0x63 0x64 0x65 0x66 0x67 0x68 0x69 0x6A 0x6B 0x6C 0x6F KP-X7 0x71 0x72 0x73 0x74 0x75 0x76 0x77 0x78 0x79 0x7A 0x7B 0x7C 0x7F The codes are loaded into the FIFO buffer in the order in which they occurred. Table 6 shows an example sequence of events, and Figure 7 shows the resulting sequence of event codes loaded into the FIFO buffer. TABLE 6. Example Sequence of Events Event Number Event Code Event on Input Driven Output Description 1 0xC5 KP-X4 KP-Y4 Key is pressed 2 0xB2 KP-X3 KP-Y1 Key is pressed 3 0x45 KP-X4 KP-Y4 Key is released 4 0x32 KP-X3 KP-Y1 Key is released 5 0x81 KP-X0 KP-Y0 Key is pressed 6 0x5F KP-X5 n.a. SF Key is released 7 0x01 KP-X0 KP-Y0 Key is released 8 0x00 n.a. n.a. Indicates end of stored events 30013607 FIGURE 7. Example Event Codes Loaded in FIFO Buffer 12.2 KEYPAD SCAN CYCLES The LM8322 starts new scan cycles at fixed time intervals of about 4 milliseconds. If a change in the state of the keypad is detected, the keypad is rescanned after a debounce delay. When the state change has been reliably captured, it is en- coded and written to the FIFO buffer. Figure 8 shows the relationship between a KP-Yx output and a KP-Xx input over multiple scan cycles during a key press event. Between scan cycles, the KP-Yx outputs that are spec- ified by the SET_KEY_SIZE command (0x90) for keypad scanning are driven low. 30013608 FIGURE 8. Keypad Scan Cycles www.national.com 14 |
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