| 摘要 |
A cardiac pacemaker includes a microprocessor 300 and a memory 302 capable of being programmed with a variety of processes for stimulating a heart and/of sensing and transmitting to an external device conditions of the heart or pacemaker. The microprocessor controls a multiplexer 306 to input signals from atrial and ventricular leads, the power source or a reed switch operable by an external magnet, on lines 338 a-f. The output comprises decoder 342 and latch 340 with output select switches 330 which are selectively operable to supply stimulation pulses to the leads or allow sensing. External apparatus 343 may transmit coded information to change the stored program or operation of the reed switch may select a different program starting address. The microprocessor 300 includes an address counter 307, and an auto reset oscillator circuit 344 periodically (e.g. every 0.5s) applies a reset signal to reset the address to the program starting address whereby if a noise signal (eg. from a defrillation pulse) causes an erroneous or meaningless memory location to be addressed the program will not 'hang up'. Reset circuit 344 is defeated during normal operation by a signal on line 346. <IMAGE> |
