Overview

Product details

The XD40192 Presettable BCD Up/Down Counter and the XD40193 Presettable Binary Up/Down Counter each consist of 4 synchronously clocked "D" type flip-flops connected as counters. Inputs include 4 separate disturb lines, a preset enable control, separate clock up and clock down signals and a master reset, four buffered Q signal outputs, and carry and borrow outputs for a multi-stage counting scheme. The counter is cleared so that all outputs are in a low state with a high value on the reset line. Resetting is done asynchronously with the clock. Each output is individually programmable and synchronized with the clock at the corresponding disturb input level when the preset enable control is low.

If the clock down line is high, the counter counts up once on the positive clock edge of the clock up signal. If the clock up line is high, the counter counts down once on the positive clock edge of the clock down signal. The carry and borrow signals are high when the counter is counting up or down. In the up-counting mode, the carry signal goes low for half a clock period after the counter reaches the maximum count. In countdown mode, the borrow signal goes low within half a clock cycle after the counter reaches the minimum count. By connecting the borrow and carry outputs to the clock falling and clock rising inputs of the subsequent counter package, respectively, multiple packages can be easily cascaded without additional external circuitry.