{"id":5736,"date":"2023-12-08T10:00:52","date_gmt":"2023-12-08T09:00:52","guid":{"rendered":"https:\/\/msxitalia.org\/?p=5736"},"modified":"2023-12-08T15:29:38","modified_gmt":"2023-12-08T14:29:38","slug":"i-registri-della-cpu-z80","status":"publish","type":"post","link":"https:\/\/msxitalia.org\/en\/i-registri-della-cpu-z80\/","title":{"rendered":"The Z80 CPU registers \u2013 handout 2"},"content":{"rendered":"

What you are about to read is a handout and certainly not a book and therefore does not claim to be exhaustive and self-sufficient. This can be accompanied by documentation that can be easily found both in paper and digital form. For the drafting of this handout, in addition to the obvious information that can be found online, I took extensive inspiration from the Z80 Programming in Assembly language manuals and the New Z80 manual. As with all my other articles I apologize for any inaccuracies. Enjoy the reading.<\/p>\n

INTERNAL STRUCTURE OF THE CPU<\/p>\n

REGISTERS
\nThe figure illustrates the register set of the Z80 CPU. All registers are implemented using static RAM. As we can see the CPU integrates two sets of six generic registers that can be used individually as 8-bit registers or in pairs as 16-bit registers and two sets of accumulator and flag registers. These, as can be seen from the figure, are called Main Register and Alternate Register. There are also six registers for special uses. Below we will see in detail the function of each register.\"Set

SPECIAL REGISTERS<\/h5>\n

Below we describe the set of registers defined as special within the Z80 CPU.<\/p>\n

PROGRAM COUNTER (PC)<\/strong>
\n\"\"

STACK POINTER (SP)
\n<\/strong>\"\"

INDEX REGISTER (IX, IY)<\/strong><\/p>\n

\"\"

INTERRUPT PAGE ADDRESS REGISTER (I)
\n<\/strong>\"\"

MEMORY REFRESH REGISTER (R)<\/strong>
\n\"\"

GENERAL USE REGISTERS<\/h5>\n

The remaining registers are divided into two interchangeable groups, one defined as the main register bank and the other as the alternative register bank (in the figure at the beginning of the handout they are shown as Main register and Alternate register but the meaning does not change). Through the exchange instructions, the programmer can select the bank of registers on which he wants to operate.<\/p>\n

ACCUMULATOR <\/strong><\/p>\n

\"\"

REGISTER FLAG
\n<\/strong>The Flag register is structured as shown in the figure, depending on the documentation you read, the memonic names may be slightly different, but their meaning remains unchanged.
\nStarting from the least significant bit we find:<\/p>\n