Epson PX-8 User Manual page 121

RSIOX tPUT)
Function: Sends one byte of data.
Entry parameters
Register B = 60H
Register C = Send data
Register HL= Address of the block which is used to store return information
Return parameters
Z flag = 1 Normal completion
Register HL= Refer to the OPEN function.
Z flag = 0 Abnormal end
Register A = 03H Interface not open
A = OOH CTRL-STOP was pressed
The contents of register HL is not changed.
RSIOX (CTLIN)
Function: Reads the status of the control line.
Entry parameter
Register B = 70H
Return parameters
Z flag = 1 Normal completion
Register A shows the conditions of the control line flags as follows:
DCD status
DRS status
Z flag = OOH Abnormal end
Register A = 03H Interface not open
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RSIOX (SETCTL)
Function: Sets the control lines.
Entry parameters
Register B = SOH
Register C = Data to be set
BIT 0 = DTR (H for "1" and L for "0")
BIT 1 = RTS (H for" 1" and L for "0")
Return parameters
Z flag = 1 Normal completion
Z flag = 0 Abnormal end
Register A = 3 Interface not open
RSIOX (ERSTS)
\
Function: Checks the error status and clears the error flags.
Entry parameter
Register B = 90H
Return parameters
Z flag = 1 Normal completion
Register A contains the conditions of the control line flags
Receive buffer overflow
DCD status
Parity error
Receive overrun
Framing error
DSR status
Z flag = OOH Abnormal end
Register A = 03H Interface not open
RSIOX (SENS)
Function: Checks the status of the RS232C interface.
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