Zilog Z80380 - Manual (Page 106)

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Z380 ™
U SER ' S M ANUAL
DC-8297-03
Z ILOG
IND
INPUT AND DECREMENT (BYTE)
IND
Operation: (HL)
←
(C)
B
←
B – 1
HL
←
HL – 1
This instruction is used for block input of strings of data. During the I/O transaction the 32-
bit BC register is placed on the address bus. Note that the B register contains the loop count
for this instruction so that A15-A8 are not useable as part of a fixed port address.
First the byte of data from the selected peripheral is loaded into the memory location
addressed by the HL register. Then the B register, used as a counter, is decremented by
one. The HL register is then decremented by one, thus moving the pointer to the next
destination for the input.
Flags: S: Unaffected
Z: Set if the result of decrementing B is zero; cleared otherwise
H: Unaffected
V: Unaffected
N: Set
C: Unaffected
Addressing Execute
Mode Syntax Instruction Format Time Note
IND 11101101 10101010 2+i+w