Rainbow Electronics АDC0805 - Manual (Page 31)

TL H 5671 – 29
FIGURE 21 Multiple A Ds with Z-80 Type Microprocessor
INTERRUPT SERVICING SUBROUTINE
SOURCE
LOC OBJ CODE STATEMENT COMMENT
0038 E5 PUSH HL Save contents of all registers affected by
0039 C5 PUSH BC this subroutine
003A F5 PUSH AF Assumed INT mode 1 earlier set
003B 21 00 3E LD (HL) X3E00 Initialize memory pointer where data will be stored
003E 0E 01 LD C X01 C register will be port ADDR of A D converters
0040 D300 OUT X00 A Load peripheral status word into 8-bit latch
0042 DB00 IN A X00 Load status word into accumulator
0044 47 LD B A Save the status word
0045 79 TEST LD A C Test to see if the status of all A D’s have
0046 FE 08 CP X08 been checked If so exit subroutine
0048 CA 60 00 JPZ DONE
004B 78 LD A B Test a single bit in status word by looking for
004C 1F RRA a ‘1‘ to be rotated into the CARRY (an INT
004D 47 LD B A is loaded as a ‘1‘) If CARRY is set then load
004E DA 5500 JPC LOAD contents of A D at port ADDR in C register
0051 0C NEXT INC C If CARRY is not set increment C register to point
0052 C3 4500 JP TEST to next A D then test next bit in status word
0055 ED 78 LOAD IN A (C) Read data from interrupting A D and invert
0057 EE FF XOR FF the data
0059 77 LD (HL) A Store the data
005A 2C INC L
005B 71 LD (HL) C Store A D identifier (A D port ADDR)
005C 2C INC L
005D C3 51 00 JP NEXT Test next bit in status word
0060 F1 DONE POP AF Re-establish all registers as they were
0061 C1 POP BC before the interrupt
0062 E1 POP HL
0063 C9 RET Return to original program
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