Cypress CY7C65113C manual Programming Model, bit Program Counter

CY7C65113C

Table 4-3. Instruction Set Summary (continued)

MNEMONIC	operand	opcode	cycles
XPAGE		1F	4
MOV A,X		40	4
MOV X,A		41	4
MOV PSP,A		60	4
CALL	addr	50-5F	10
JMP	addr	80-8F	5
CALL	addr	90-9F	10
JZ	addr	A0-AF	5 (or 4)
JNZ	addr	B0-BF	5 (or 4)

MNEMONIC	operand	opcode	cycles
RET		3F	8
DI		70	4
EI		72	4
RETI		73	8
JC	addr	C0-CF	5 (or 4)
JNC	addr	D0-DF	5 (or 4)
JACC	addr	E0-EF	7
INDEX	addr	F0-FF	14

5.0Programming Model

5.114-bit Program Counter

The 14-bit Program Counter (PC) allows access to up to 8 KB of PROM available with the CY7C65113C architecture. The top 32 bytes of the ROM in the 8K part are reserved for testing purposes. The program counter is cleared during reset, such that the first instruction executed after a reset is at address 0x0000h. Typically, this is a jump instruction to a reset handler that initializes the application (see Interrupt Vectors on page 25).

The lower eight bits of the program counter are incremented as instructions are loaded and executed. The upper six bits of the program counter are incremented by executing an XPAGE instruction. As a result, the last instruction executed within a 256-byte “page” of sequential code should be an XPAGE instruction. The assembler directive “XPAGEON” causes the assembler to insert XPAGE instructions automatically. Because instructions can be either one or two bytes long, the assembler may occasionally need to insert a NOP followed by an XPAGE to execute correctly.

The address of the next instruction to be executed, the carry flag, and the zero flag are saved as two bytes on the program stack during an interrupt acknowledge or a CALL instruction. The program counter, carry flag, and zero flag are restored from the program stack during a RETI instruction. Only the program counter is restored during a RET instruction.

The program counter cannot be accessed directly by the firmware. The program stack can be examined by reading SRAM from location 0x00 and up.

Document #: 38-08002 Rev. *D Page 11 of 49

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