Registers; Figure 2.1.2A Special Registers - Fujitsu F2MC-16LX MB90580 Series Hardware Manual

2.1 CPU

2.1.2 Registers

2
The F MC-16LX registers are largely classified into two types: special registers in the CPU and
general-purpose registers in memory. The special registers are dedicated internal hardware of the CPU,
and their applications are limited by the CPU architecture. The general-purpose registers share the CPU
address space with RAM. The general-purpose registers are the same as the special registers in that they
can be accessed without using an address. The applications of the general-purpose registers can be
specified by the user however, as is ordinary memory space.
Special registers
2
The F MC-16LX has the following 13 special registers:
• Accumulator (A=AH:AL): Two 16-bit accumulators (Can be used as a single 32-bit accumulator.)
• User stack pointer (USP): 16-bit pointer indicating the user stack area
• System stack pointer (SSP): 16-bit pointer indicating the system stack area
• Processor status (PS): 16-bit register indicating the system status
• Program counter: 16-bit register holding the address of the program
• Program bank register: 8-bit register indicating the PC space
• Data bank register: 8-bit register indicating the DT space
• User stack bank register (USB): 8-bit register indicating the user stack space
• System stack bank register (SSB): 8-bit register indicating the system stack space
• Additional bank register (ADB): 8-bit register indicating the AD space
• Direct page register (DPR): 8-bit register indicating a direct page
32 bit
20 Chapter 2: CPU
AH
AL
USP
SSP
PS
PC
16 bit

Figure 2.1.2a Special registers

Accumulator
User stack pointer
System stack pointer
Processor status
Program counter
DRP
Direct page register
PCB
Program bank register
DTB Data bank register
USB User stack bank register
SSB System stack bank register
ADB Additional data bank register
8 bit
MB90580 Series