RCA CDP18S711 manual Operating System Register Table, Operating System Summary

34 RCA COSMAC VIP Instruction Manual

Operating System Register Table

Memory	Register	Memory	Register
Address	Byte	Address	Byte,
0XB0		0XC0
0XB1		0XC1
0XB2		0XC2
0XB3	R3.0	0XC3	R3.1
0XB4	R4.0	0XC4	R4.1
0XB5	R5.0	0XC5	R5.1
0XB6	R6.0	0XC6	R6.1
0XB7	R7.0	0XC7	R7.1
0XB8	R&0	0XC8	R8.1
0XB9	R9.0	0XC9	R9.1
0XBA	RA.0	0XCA	RA.1
0XBB	RB.0	0XCB	RB.1
0XBC	RC.0	0XCC	RC.1
0XBD	RD.0	0XCD	RD.1
0XBE	RE.0	0XCE	RE.1
0XBF	RF.0	0XCF	RF.1

0X = 07 for 2048-byte RAM

0X = 0B for 3072-byte RAM

0X = 0F for 4096-byte RAM

R5 = CHIP-8 language program counter RA = CHIP-8 language I pointer

R3 = Machine Language Subroutine Program Counter

Operating System Summary

1.RUN up with key C pressed selects operating system at 8000.

2.Enter four-digit address followed by mode digit:

AMR (Memory Read)

0 MW (Memory Write)

BTR (Tape Read)

FTW (Tape Write)

3.CDP1802 microprocessor registers are stored as shown in table above. They may be examined after a program is run by using operating system mode A.

4.Mode 0 can be used to insert temporary stops in a program for debugging purposes. Insert a "branch-to-itself" instruction at the desired stopping point.

5.The operating system uses the top 84 bytes of RAM (0XAC-0XFF). Avoid using these byte locations in your programs.

6.The operating system searches for and uses the top (highest) 256-byte page of on-card RAM. When RUN is flipped up to execute a program, beginning at 0000, the following initial conditions exist:

P=0, Q=0, R0=0000, and R1 =0XFF where 0X highest page of on-card RAM.