Datasheet

Thursday, 17 July 2003 MiniProject: Design Aspects Colin K McCord
EEE512J2 – Electronic Product Design Page 26 Chapter 5: System Architecture
5.0. SYSTEM ARCHITECTURE
5.1. System Block Diagram
The proposed design is shown in block diagram form in figure 5.1a, it is clear that there are two main
features: displaying the ECG on a CRT display (e.g. use an oscilloscope) and transmitting the data to a PC
in real-time to display and log ECG data.
PIC16F877
(Microcontroller)
20 MHZ ClockRxD
TxD
0Æ 5V
MAX232
(Line Buffer)
M6264P-15
(RAM)
ECG
ECG
Amplifer
A[7..0] D[7..0]
/WE
/OE
RA2
RA3
PC for data logging /
displaying ECG
Analogue oscilloscope operating in XY mode for
displaying ECG
RA4 RA5
/A or B
/Enable
ZN508E-8
(Dual DAC)
VA Out
VB Out
Port D Port BADC
Figure 5.1a. Simplified block diagram of the system
Obviously the design of a Windows based software application is required to log and display ECG signals
directly from the serial port. This application should be user-friendly, i.e. easy-to-use using standard
Windows interface dialog controls (users are familiar with these controls). Clearly since serial communication
is used a simple but effective communication protocol is required.
The heart of the system is the PIC16F877 microcontroller: “The PIC16F877 is a high-performance FLASH
microcontroller that provides engineers with the highest design flexibility possible. In addition to 8192x14