User`s manual

DIGITAL-LOGIC AG MSLB-P5 Manual V0.3
PRELIMINARY 177
16.6.9 Interrupt 14h–Serial Services
The INT 14 software interrupt handles serial I/O service requests. Use the AH register to specify the
service to invoke. This describes the UART Modem and Line Status returned by these services. It also
includes two services, 04h and 05h, that support the extended communication capabilities of PS/2.
The following describes the modem status returned by serial services.
Modem Status
AL Description
Bit 0 1 = Delta clear to send
Bit 1 1 = Delta data set ready
Bit 2 1 = Trailing edge ring indicator
Bit 3 1 = Delta data carrier detect
Bit 4 1 = Clear to send
Bit 5 1 = Data set ready
Bit 6 1 = Ring indicator
Bit 7 1 = Received line signal detect
The following describes the line status returned by Int 14h Serial Services.
Line Status
AH Description
Bit 0 1 = Data ready
Bit 1 1 = Overrun error
Bit 2 1 = Parity error
Bit 3 1 = Framing error
Bit 4 1 = Break detect
Bit 5 1 = Trans holding register empty
Bit 6 1 = Trans shift register empty
Bit 7 1 = Time out error
The following describes the serial communication services of PhoenixBIOS 4.0:
Interrupt 14h Serial Services
AH = 00 Initialize Serial Adapter
Entry:
AL Init parameters:
Bit 1,0 10 = 7 data bits
11 = 8 data bits
Bit 20 = 1 stop bit
1 = 2 stop bits
Bit 4,3 00 = No parity
10 = No parity
01 = Odd parity
11 = Even parity
Bit 7-5 000 = 110 Baud- 417 divisor
001 = 150 Baud-300 divisor
010 = 300 Baud-180 divisor
011 = 600 Baud-0C0 divisor
100 = 1200 Baud-060 divisor
101 = 2400 Baud-030 divisor
110 = 4800 Baud-018 divisor
111 = 9600 Baud-00C divisor
DX Serial port (0-3)
Exit:
AL Modem status
AH Line status