SYSTEM CONFIGURATION332.10 Program Memory and External Data Memory2.10.1 MSM80C154S/MSM83C154S program area and external ROM connectionsSince MSM80C154S/MSM83C154S are equipped with a 16-bit program counter, thesedevices can execute programs of up to 64K bytes (including both internal and externalprograms).Since the MSM80C154S is not equipped with an internal program ROM, however, onlyexternal instructions are executed. MSM83C154S, on the other hand, is equipped with a 16Kbyte program ROM which enables it to execute internal instructions from address 0 thruaddress 16383. External instructions are executed when the address is greater than 16383.The program area is outlined in Figure 2-24, and a diagram of ROM connections made whenexternal instructions are executed is shown in Figure 2-25.Timer interrupt 2 start address 43 002BHSerial I/O interrupt start address 35 0023HTimer interrupt 1 start address 27 001BHExternal interrupt 1 start address 19 0013HTimer interrupt 0 start address 11 000BHExternal interrupt 0 start address 3 0003H2 0002H1 0001HCPU reset start address 0 0000H7 6 5 4 3 2 1 0002BH43002CH443FFFH163834000H163840FFFFH655350MSM80C154S external ROM areaMSM83C154S internal ROM area MSM83C154S external ROM areaFigure 2-24 MSM80C154S/MSM83C154S program area
