8254 Programmable Interval Timer/Counter
Features
- Status read-back command
- Counter latch command
- Read/write least significant bit (LSB) only, most significant bit (MSB) only, or LSB first then MSB
- Six programmable counter modes
- Interrupt on terminal count
- Hardware retriggerable one-shot
- Rate generator
- Square wave mode
- Software-triggered strobe
- Hardware-triggered strobe (retriggerable)
- Binary or binary coded decimal strobe
- Developed in VHDL and synthesizes to approximately 5,000 gates
- Functionally based on the Intel 82C54 device
Block Diagram
Figure 1 shows the block diagram for the 8254 programmable interval timer/counter megafunction.
| Figure 1. Block Diagram |
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Description
The 8254 programmable interval time/counter megafunction is a high-performance function that is designed to solve the common timing control problems in microcomputer system design. It provides three independent 16-bit counters, and each counter may operate in a different mode. All modes are software programmable. The 8254 megafunction 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 8254 megafunction can be programmed to match requirements by programming one of the counters for the desired delay.
Device Utilization Example
Table 1 lists the typical device utilization results for the megafunction.
| Table 1. Typical Device Utilization for the Megafunction |
| Device |
Speed Grade |
Utilization |
Performance
(fMAX) |
Parameter Setting |
| Logic Elements (1) |
EABs (2) |
| Cyclone™ EP1C20 |
-6 |
524 |
- |
109 MHz |
Contact CAST |
| Stratix™ EP1S20 |
-5 |
524 |
- |
119 MHz |
Contact CAST |
| Stratix II EP2S60 |
-3 |
536 |
- |
166 MHz |
Contact CAST |
Notes to Table 1:
- The LE count for Stratix II devices is based on the number of adaptive look-up tables (ALUTs) used for the design as reported by the Quartus® II software.
- EABs = Embedded array blocks
Contact Information
For additional information, you can contact CAST, Inc. at:
CAST, Inc.
11 Stonewall Court
Woodcliff Lake, NJ 07677, USA
Phone: +1 (845) 353-6160
Fax: +1 (845) 727-7607
E-mail: OpenCore@cast-inc.com
WWW: http://www.cast-inc.com
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