Intel mcs-48 manual SEL MBO Select Memory Bank, JMP $+20, Jump to Location, 48 HEX

INSTRUCTION SET

SEL MBO Select Memory Bank 0 (Not in 8021, 8022)

11110101011

PC bit 11 is set to zero on next JMP or CALL instruction. All references to program memory addresses fall within the range 0-2047.

(DBF) .... 0

Example: Assume program counter contains 834 Hex.

SEL MBO	;SELECT MEMORY BANK 0
JMP $+20	;JUMP TO LOCATION
	;48 HEX

SEL MB1 Select Memory Bank 1 (Not in 8021, 8022) 11111101011

PC bit 11 is set to one on next JMP or CALL instruction. All references to program memory addresses fall within the range 2048-4095.

(DBF) .... 1

SEL RBO Select Register Bank 0 (Not in 8021, 8022)

11100101011

PSW bit 4 is set to zero. References to working registers 0-7 address data memory locations 0-7. This is the recommended setting for normal program execution.

(BS) .... 0

SEL RB1 Select Register Bank 1 (Not in 8021, 8022)

11101101011

PSW bit 4 is set to one. References to working registers 0-7 address data memory locations 24-31. This is the recommended setting for interrupt service routines, since locations 0-7 are left intact. The setting of

PSW bit 4 in effect at the time of an interrupt is restored by the RETR instruction when the interrupt service routine is completed.

(BS) .... 1

Example: Assume an external interrupt has occurred, control has passed to program memory location 3, and PSW bit 4 was zero before the interrupt.

LOC3: JNI INIT	;JUMP TO ROUTINE 'INIT'IF
	;INTERRUPT INPUT IS ZERO

Mnemonics copyright Intel Corporation 1976.

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