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HS-82C54RH Datasheet(PDF) 6 Page - Intersil Corporation |
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HS-82C54RH Datasheet(HTML) 6 Page - Intersil Corporation |
6 / 17 page 6 Functional Description General The HS-82C54RH is a programmable interval timer/counter designed for use with microcomputer systems. It is a general purpose, multi-timing element that can be treated as an array of I/O ports in the system software. The HS-82C54RH solves one of the most common problems in any microcomputer system, the generation of accurate time delays under software control. Instead of setting up timing loops in software, the programmer configures the HS-82C54RH to match his requirements and programs one of the counters for the desired delay. After the desired delay, the HS-82C54RH will interrupt the CPU. Software overhead is minimal and variable length delays can easily be accommodated. Some of the other timer functions common to micro- computers which can be implemented with the HS-82C54RH are: • Real time clock • Event counter • Digital one-shot • Programmable rate generator • Square wave generator • Binary rate multiplier • Complex waveform generator • Complex motor controller Data Bus Buffer This three-state, bi-directional, 8-bit buffer is used to interface the HS-82C54RH to the system bus (see Figure 5). Read/Write Logic The Read/Write Logic accepts inputs from the system bus and generates control signals for the other functional blocks of the HS-82C54RH. A1 and A0 select one of the three counters or the Control Word Register to be read from/written into. A “low” on the RD input tells the HS-82C54RH that the CPU is reading one of the counters. A “low” on the WR input tells the HS-82C54RH that the CPU is writing either a Control Word or an initial count. Both RD and WR are qualified by CS; RD and WR are ignored unless the HS-82C54RH has been selected by holding CS low. Control Word Register The Control Word Register (Figure 6) is selected by the Read/Write Logic when A1, A0 = 11. If the CPU then does a write operation to the HS-82C54RH, the data is stored in the Control Word Register and is interpreted as a Control Word used to define the Counter operation. The Control Word Register can only be written to; status information is available with the Read-Back Command. Counter 0, Counter 1, Counter 2 These three functional clocks are identical in operation, so only a single Counter will be described. The internal block diagram of a single counter is shown in Figure 7. The counters are fully independent. Each Counter may operate in a different Mode. The Control Word Register is shown in the figure; it is not part of the Counter itself, but its contents determine how the Counter operates. (8) CONTROL WORD REGISTER D7-D0 RD WR A0 A1 CS COUNTER 1 COUNTER 0 COUNTER 2 OUT 1 GATE 1 CLK 1 OUT 0 GATE 0 CLK 0 OUT 2 GATE 2 CLK 2 DATA BUS BUFFER READ/ WRITE LOGIC FIGURE 5. DATA BUS BUFFER AND READ/WRITE LOGIC FUNCTION (8) DATA BUS BUFFER READ/ WRITE LOGIC CONTROL WORD REGISTER D7-D0 RD WR A0 A1 CS COUNTER 1 COUNTER 0 COUNTER 2 OUT 1 GATE 1 CLK 1 OUT 0 GATE 0 CLK 0 OUT 2 GATE 2 CLK 2 FIGURE 6. CONTROL WORD REGISTER AND COUNTER FUNCTIONS HS-82C54RH |
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