SRC

Name

Send Register Control

Function

The 8 bits contained in the register pair specified by RP are used
as an address. This address may designate a particular DATA RAM
data character, a DATA RAM status character, a RAM output port, or
a ROM input/output port.

Syntax

SRC(RPp)

Assembled

Binary

0010RPp1

Decimal

33, then incrementing by 2 until 47 (1st word)

Hexadecimal

0x21, then incrementing by 2 until 0x2F (1st word)

Symbolic

 ../../_images/src-sym.png

Execution

1 words, 8-bit code and an execution time of 10.3 \({\mu}\) sec

Side-effects

Not Applicable

Implemented

src

Detailed Description

The address contained within the specified register pair designates either a particular DATA RAM data character, a DATA RAM status character, a RAM output port, or a ROM input/output port. However, the address designates all of these simultaneously; it is up to the programmer to then write the correct I/O or RAM instruction to access the proper entity.

The disassembly of the instruction below shows how the register pair are represented in the opcode.

../../_images/src.png

The address sent by the SRC remains in effect until changed by a subsequent SRC.

The only DATA RAM bank which receives the SRC address is the one selected by the last previous DCL instruction.

The 8 bits of the address sent by the SRC are interpreted in one of four ways, depending on the context as follows:

When referring to a DATA RAM Character

../../_images/src-dataram-char.png

When referring to a DATA RAM Status Character

../../_images/src-dataram-status.png

When referring to a DATA RAM Output Port

../../_images/src-dataram-output.png

When referring to a ROM I/O Port

../../_images/src-rom-io.png

Example program

/ Example program
        org    ram
        fim    1p  180
        src    1p
        end