GENERAL DESCRIPTION

The TM8721 is an embedded high-performance 4-bit microcomputer with LCD driver. It contains all the of the following functions in a single chip: 4-bit parallel processing ALU, ROM, RAM, I/O ports, timer, clock generator, dual clock operation, Resistance to Frequency Converter (RFC), LCD driver, look-up table. 

BLOCK DIAGRAM

FEATURE

1. Powerful instruction set (137 instructions) 

• Binary addition, subtraction, BCD adjust, logical operation in direct and 

• index addressing mode. 

• Single-bit manipulation. (set, reset, decision for branch) 

• Various conditional branch. 

• 16 working registers and manipulation. 

• Look-up table. 

• LCD driver data transfer. 

2. Memory capacity 

• ROM capacity       1024 x 16 bits. 

• RAM capacity       64 x 4 bits.

3. Input/output ports 

• Port IOA4        1 pin (with internal pull-low).

  IOA4 port had built in the input signal  chattering prevention circuitry.

• Port IOC          4 pins (with internal pull-low, low-level-hold).

• Port IOB3,4      2 pins (with internal pull-low), & mask option with BZB, BZ. 

4. 8 level subroutine nesting. 
5. Interrupt function 

• External factor      1     (Pin IOA4 port). 

• Internal factors     3     (Pre-Divider, Timer2 & RFC). 

6. Built in Alarm, clock or single tone melody generator (BZB, BZ), & mask option with IOB3, 4. 
7. Built-in R to F Converter circuit 

• CX, RR, RT. 

8. One 6-bit programmable timer (Timer 2) with programmable clock source. 
9. LCD driver output 

• 9 LCD driver outputs. (Up to drive 36 LCD segments) 

• 1/4 Duty and 1/2 Bias for LCD display. 

• Single instruction to turn off all segments. 

• 9 DC/Open Drain outputs for LED mask option. 

• 16 LCD Address. 

10. Built-in Voltage double charge pump circuit. 
11. Clock oscillation can be defined as X’tal, external-R or internal-R 2 type oscillator by mask option. 
12. HALT function. 
13. STOP function.