Specifications

S1C62N82 TECHNICAL SOFTWARE EPSON II-21
CHAPTER 3: PERIPHERAL CIRCUITS (Input Ports)
• Loading K00–K03 into the A register
Label Mnemonic/operand Comment
LD Y,0E0H ;Set address of port
LD A,MY ;A register ← K00–K03
As shown in Figure 3.2.1, the two instruction steps above
load the data of the input port into the A register.
Examples of input
port control
program
D3
K03
D2
K02
D1
K01
D0
K00
A register
Fig. 3.2.1
Loading the A register
The data of the input port can be loaded into the B register
or MX instead of the A register.
• Bit-unit checking of input ports
Label Mnemonic/operand Comment
DI ;Disable interrupt
LD Y,0E0H ;Set address of port
INPUT1: FAN MY,0010B ;
JP NZ,INPUT1 ;Loop until K01 becomes "0"
INPUT2: FAN MY,0010B ;
JP Z,INPUT2 ;Loop until K01 becomes "1"
This program loopes until a rising edge is input to input port
K01.
The input port can be addressed using the X register instead
of the Y register.
When the input port is changed from high level to low level with a
pull-down resistor, the signal falls following a certain delay caused
by the time constants of the pull-down resistance and the input
gate capacitance. It is therefore necessary to observe a proper
wait time before the input port data is read.
Note