//74LS193 具有双时钟和清零功能的同步 4 位加/减二进制计数器
//4-bit synchronous binary up/down counter
// Synchronous reversible 4-bit binary counting
// Asynchronous parallel load
// Asynchronous reset
// Pin No. Pin Name Description
// 1 D1 data input 1
// 2 Q1 flip-flop output 1
// 3 Q0 flip-flop output 0
// 4 CPD count down clock input
// 5 CPU count up clock input
// 6 Q2 flip-flop output 2
// 7 Q3 flip-flop output 3
// 8 GND ground (0V)
// 9 D3 data input 3
// 10 D2 data input 2
// 11 PL — asynchronous parallel load input (active LOW)
// 12 TCU — terminal count up (carry) output (active LOW)
// 13 TCD — terminal count down (borrow) output (active LOW)
// 14 MR asynchronous master reset input (active HIGH)
// 15 D0 data input 0
// 16 VCC supply voltage
// Note: CPD, CPU is LOW-to-HIGH, edge triggered.
// 74LS193功能表 Function Table
// |----------------------------------------------------------------------------------------|
// | 操作模式 | 输入 Input | 输出 Output |
// | Operating |------------------------------------------|---------------------------------|
// | mode | MR | ~PL | CPU | CPD | D0 | D1 | D2 | D3 | Q0 | Q1 | Q2 | Q3 | ~TCU | ~TCD |
// |-----------|----------------------------------------------------------------------------|
// | Reset | H | X | X | L | X | X | X | X | L | L | L | L | H | L |
// | |------------------------------------------|---------------------------------|
// | (clear) | H | X | X | H | X | X | X | X | L | L | L | L | H | H |
// |-----------|------------------------------------------|---------------------------------|
// | Parallel | L | L | X | L | L | L | L | L | L | L | L | L | H | L |
// | |------------------------------------------|---------------------------------|
// | | L | L | X | H | L | L | L | L | L | L | L | L | H | H |
// | |------------------------------------------|---------------------------------|
// | | L | L | L | X | H | H | H | H | H | H | H | H | L | H |
// | |------------------------------------------|---------------------------------|
// | load | L | L | H | X | H | H | H | H | H | H | H | H | H | H |
// |-----------|------------------------------------------|---------------------------------|
// | Count up | L | H | ↑ | H | X | X | X | X | count up | H | H |
// |-----------|------------------------------------------|---------------------------------|
// |Count down | L | H | H | ↑ | X | X | X | X | count down | H | H |
// |-----------|------------------------------------------|---------------------------------|