Microprocessor architecture programming and applications with the 8085 pdf

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Please forward this error screen to 158. Unsourced material may be challenged and removed. microprocessor architecture programming and applications with the 8085 pdf V supplies needed by the 8080. 8080-derived CPU introduced the year before.

However, an 8085 circuit requires an 8-bit address latch, so Intel manufactured several support chips with an address latch built in. O and 5 prioritized interrupts, arguably microcontroller-like features that the Z80 CPU did not have. 1970s, the 8085 served for new production throughout the lifetime of those products. This was typically longer than the product life of desktop computers.

State signals are provided by dedicated bus control signal pins and two dedicated bus state ID pins named S0 and S1. Pin 39 is used as the Hold pin. Only a single 5 volt power supply is needed, like competing processors and unlike the 8080. Intel 8155, 8355, and 8755 memory chips allow a direct interface, so an 8085 along with these chips is almost a complete system. Each of these five interrupts has a separate pin on the processor, a feature which permits simple systems to avoid the cost of a separate interrupt controller.

All interrupts are enabled by the EI instruction and disabled by the DI instruction. 8085 that are not from the 8080 design, allow each of the three maskable RST interrupts to be individually masked. All three are masked after a normal CPU reset. SIM and RIM also allow the global interrupt mask state and the three independent RST interrupt mask states to be read, the pending-interrupt states of those same three interrupts to be read, the RST 7. SOD and SID pins, respectively, all under program control and independently of each other. O or memory-mapped port, e. 14 MHz crystal would yield a 3.

The internal clock is available on an output pin, to drive peripheral devices or other CPUs in lock-step synchrony with the CPU from which the signal is output. 8080 can run directly on the 8085 without translation or modification. Exceptions include timing-critical code and code that is sensitive to the aforementioned difference in the AC flag setting or differences in undocumented CPU behavior. 8085 differs from the published specifications, especially in subtle details. The same is not true of the Z80. As mentioned already, only the SIM and RIM instructions were new to the 8085.

A, B, C, D, E, H, and L, where A is also known as the accumulator. As in the 8080, the contents of the memory address pointed to by HL can be accessed as pseudo register M. The auxiliary or half carry flag is set if a carry-over from bit 3 to bit 4 occurred. The zero flag is set if the result of the operation was 0. Some of them are followed by one or two bytes of data, which can be an immediate operand, a memory address, or a port number.

A NOP “no operation” instruction exists, but does not modify any of the registers or flags. 16-bit register-pair on the machine stack. These are intended to be supplied by external hardware in order to invoke a corresponding interrupt-service routine, but are also often employed as fast system calls. One sophisticated instruction is XTHL, which is used for exchanging the register pair HL with the value stored at the address indicated by the stack pointer. For two-operand 8-bit operations, the other operand can be either an immediate value, another 8-bit register, or a memory cell addressed by the 16-bit register pair HL. The only 8-bit ALU operations that can have a destination other than the accumulator are the unary incrementation or decrementation instructions, which can operate on any 8-bit register or on memory addressed by HL, as for two-operand 8-bit operations. Direct copying is supported between any two 8-bit registers and between any 8-bit register and a HL-addressed memory cell, using the MOV instruction.

An immediate value can also be moved into any of the foregoing destinations, using the MVI instruction. Although the 8085 is an 8-bit processor, it has some 16-bit operations. LHLD loads HL from directly addressed memory and SHLD stores HL likewise. The XCHG operation exchanges the values of HL and DE. Adding HL to itself performs a 16-bit arithmetical left shift with one instruction. 24-bit or larger additions and left shifts. A stack frame can be allocated using DAD SP and SPHL, and a branch to a computed pointer can be done with PCHL.

16-bit variables and produce 8085 machine code. Subtraction and bitwise logical operations on 16 bits is done in 8-bit steps. A number of undocumented instructions and flags were discovered by two software engineers, Wolfgang Dehnhardt and Villy M. Sorensen in the process of developing an 8085 assembler. These instructions use 16-bit operands and include indirect loading and storing of a word, a subtraction, a shift, a rotate, and offset operations.

Output instructions—taking port addresses as operands. O mapping scheme is regarded as an advantage, as it frees up the processor’s limited address space. O address is output by the CPU on both the lower and upper halves of the 16-bit address bus. Intel produced a series of development systems for the 8080 and 8085, known as the MDS-80 Microprocessor System. The original development system had an 8080 processor. CPU, monitor, and a single 8-inch floppy disk drive. Later an external box was made available with two more floppy drives.

This unit uses the Multibus card cage which was intended just for the development system. A surprising number of spare card cages and processors were being sold, leading to the development of the Multibus as a separate product. The later iPDS is a portable unit, about 8″ x 16″ x 20″, with a handle. It can also accept a second 8085 processor, allowing a limited form of multi-processor operation where both processors run simultaneously and independently. 20 mA current loop serial interface. Counter can be optionally added.