AC architecture to rapidly change pro- gram counter assignments from one register to another. This in- truction causes a jump to the instruction sequence beginning at M R N. R 3 contains the return GLO R6. The programmer must make sure that the stack pointer is initialized to an appropriate high address memory location before an instruction that uses the stack is executed. The sequential logic states of one of the EF lines may represent a bit-serial character. Otherwise, the next instruction in sequence is fetched and executed.

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Set stack pointer Datasehet 2 to a RAM area: Ill provides the timing relationships for input instructions. Assume next that t he s witch is activated so that EFT becomes true i. The symbolic form, shown in Fig. Although Microprocessor cost is only a small part of total system or product cost memory, input, output, power-supply, system-control, and design costs are also major considerationsa unique set of COSMAC features combine to minimize the total system cost. Reference to the section on Timing Diagrams will be helpful in reading this material.

Both the receiver and datxsheet arc double buffered. The register assignments are given in Fig. In immediate addressing, R P addresses memory so dataaheet the operand is the byte following the instruction. These programs, called editors, text editors, or paper tape editors make it possible to compose assembly datashewt programs on-line, or on a stand-alone system.

If P 1 1 R P is used as the pointer to the operand, it points to the byte in memory after the instruction, called the immediate byte. The D byte is one operand, and the memory byte fd following the FC instruction is the other operand.

Users of certain Hewlett Packard calculators will be familiar with the idea that a stack can be used to organize a very complicated calculation. Because the interrupt mechanism stores X and P in the temporary register T and is typi- cally followed by the execution of SAV instruction, M R 2 contains the value of X and P at the time of interrupt.

Multiple Program Counters A program counter is a register dayasheet points to the next, instruction to be fetched and executed. MAC architecture, any one of the bit scratch-pad registers can be used as a program counter.

The low -order byte A. The datasheer branch instructions 34, 35, 36, 37, 3C, 3D, 3E. The simplest form of input to the microprocessor utilizes one of the four externa!

SKiP the next instruction UP:! If tile test condition is not met, normal program execution continues. For most instructions, the execution requires two machine cycles. The individual bits in the control byte set up the system mode according to the bit pat- tern. A location specified by the user at which program execution real or simulated is to terminate. The most frequent byte size is 8 bits. An appropriate data strobe can be generated by the user durin g S2 when TPB is true.

Note that all the examples illustrate action only during the instruction execute cycle, SI. The in- struction will be executed during the next machine cycle, state SIwhich is a memory write cycle. This method can be used for interfacing a Teletype, printer, or cd peripheral with a serial interface. If the programmer does not use tliis register datqsheet any daatsheet purpose than to point to the sub- routine, the initialization procedure need be done only once.

The value of the hex digit contained in register P determines which scratch-pad register is currently being used as the pro- gram counter. This capability is often useful as a debugging aid. The user is then free to enable the out- put of the register. For instance, in the instruction lequence C85A2B23, the instruction to be executed following C8 is The program counter is also incremented by 1.

Intersil Corp. CD Datasheet. If the subroutine needs to call other subroutines, it may call by executing a SEP R4, adtasheet. These systems may be either special datssheet general purpose in nature. In other words, the address of the immediate byte determines the page to which a branch takes place. Another application is the control of an external relay or lamp. Operations that can be performed include: Executing 74 or 7C allows a carry-in from a previous addition, thus facilitating multibyte datashset.

The programmer should choose and program a set of instructions suitable to his specific application. The short branch instruction 3C will test the status of the EFl flag. Then, the high-order branch address is read during the first execute cycle and loaded into R P. Register P has been previously set to 1designating R l as the current program counter. Instruction Set i iming The timing diagram in Fig.

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Fenriramar In the latter case, the branch address is read from memory during the SI state and transferred over the bus to R P. The call subroutine starts running in R. A final borrow is comple- mented and stored in DF. Electronic component inventory — TAMI This execution will load the successive data bytes into the D register for use by the subroutine and increment R 6 datashedt to the proper address for a return operation.


Vushicage Bytes are transmitted to and from memory by means of the common data bus. The result is too big for the 8-bit register, and a carry is generated. Just as with a real program counter, pseudo branch instructions may affect the nor- ma! The better a programmer Ci ganiz. RI2l 00 32 R! After an input device is selected, a 6A instruction could be executed to obtain a status byte from a selected device.

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