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IP82C54-10 Datasheet(PDF) 5 Page - Intersil Corporation |
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IP82C54-10 Datasheet(HTML) 5 Page - Intersil Corporation |
5 / 17 page 4-5 Operational Description General After power-up, the state of the 82C54 is undefined. The Mode, count value, and output of all Counters are undefined. How each Counter operates is determined when it is pro- grammed. Each Counter must be programmed before it can be used. Unused counters need not be programmed. Programming the 82C54 Counters are programmed by writing a Control Word and then an initial count. All Control Words are written into the Control Word Register, which is selected when A1, A0 = 11. The Control Word spec- ifies which Counter is being programmed. By contrast, initial counts are written into the Counters, not the Control Word Register. The A1, A0 inputs are used to select the Counter to be written into. The format of the initial count is determined by the Control Word used. FIGURE 4. 82C54 SYSTEM INTERFACE Write Operations The programming procedure for the 82C54 is very flexible. Only two conventions need to be remembered: 1. For Each Counter, the Control Word must be written before the initial count is written. 2. The initial count must follow the count format specified in the Control Word (least significant byte only, most significant byte only, or least significant byte and then most significant byte). Since the Control Word Register and the three Counters have separate addresses (selected by the A1, A0 inputs), and each Control Word specifies the Counter it applies to (SC0, SC1 bits), no special instruction sequence is required. Any programming sequence that follows the conventions above is acceptable. Control Word Format A1, A0 = 11; CS = 0; RD = 1; WR = 0 D7 D6 D5 D4 D3 D2 D1 D0 SC1 SC0 RW1 RW0 M2 M1 M0 BCD ADDRESS BUS (16) CONTROL BUS DATA BUS (8) I/OR I/OW WR RD CS A0 A1 A1 A0 8 COUNTER 0 OUT GATE CLK COUNTER 1 COUNTER 2 OUT GATE CLK OUT GATE CLK D0 - D7 82C54 SC - Select Counter SC1 SC0 0 0 Select Counter 0 0 1 Select Counter 1 1 0 Select Counter 2 1 1 Read-Back Command (See Read Operations) RW - Read/Write RW1 RW0 0 0 Counter Latch Command (See Read Operations) 0 1 Read/Write least significant byte only. 1 0 Read/Write most significant byte only. 1 1 Read/Write least significant byte first, then most significant byte. M - Mode M2 M1 M0 0 0 0 Mode 0 0 0 1 Mode 1 X 1 0 Mode 2 X 1 1 Mode 3 1 0 0 Mode 4 1 0 1 Mode 5 BCD - Binary Coded Decimal 0 Binary Counter 16-bit 1 Binary Coded Decimal (BCD) Counter (4 Decades) NOTE: Don’t Care bits (X) should be 0 to insure compatibility with future products. Possible Programming Sequence A1 A0 Control Word - Counter 0 1 1 LSB of Count - Counter 0 0 0 MSB of Count - Counter 0 0 0 Control Word - Counter 1 1 1 LSB of Count - Counter 1 0 1 MSB of Count - Counter 1 0 1 Control Word - Counter 2 1 1 LSB of Count - Counter 2 1 0 MSB of Count - Counter 2 1 0 Possible Programming Sequence A1 A0 Control Word - Counter 0 1 1 Control Word - Counter 1 1 1 Control Word - Counter 2 1 1 LSB of Count - Counter 2 1 0 82C54 |
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Similar Description - IP82C54-10 |
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