Fujitsu F2MC-8FX manual Structure of Program Status PS

CHAPTER 3 REGISTERS

3.4Program Status (PS)

The program status (PS) is a 16-bit application-specific register existing in the CPU. In upper byte of program status (PS), the upper 5-bit is the register bank pointer (RP) and lower 3-bit is the direct bank pointer (DP). The lower byte of program status (PS) is the condition code register (CCR). The upper byte of program status (PS), i.e. RP and DP, is mapped to address 0078H. So it is possible to make read and write accesses to them by an access to address 0078H.

■Structure of Program Status (PS)

Figure 3.4-1shows the structure of the program status.

The register bank pointer (RP) indicates the address of the register bank currently in use. The relationship between the contents of the register bank pointer and actual addresses is as shown in Figure 3.4-2.

DP shows the memory area (direct bank) used for direct addressing and bit direct addressing. Conversion from the operand address of direct addressing and bit direct addressing to the real address follows the conversion rule shown in Table 3.4-1by using DP.

The condition code register (CCR) has bits for indicating the result of operations and the content of transfer data and bits for controlling the operation of the CPU in the event of an interrupt.

Figure 3.4-1 Structure of Program Status (PS)

15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

PS

RP

DP

H I

IL0, 1 N Z V C

RP DP CCR

Figure 3.4-2 Conversion Rule for Actual Address of General-purpose Register Area

"0" "0" "0" "0" "0" "0" "0" "1"

RP Lower bits of OP code

R4 R3 R2 R1 R0 b2 b1 b0

Transaction address A15 A14 A13 A12 A11 A10 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0

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