Intel 386 User Manual

7-17
SYSTEM MANAGEMENT MODE
---------------------------------------------------------------------------*/
void SerialWriteStr2()
/* Loops while writing a char out to the serial port */
{
_asm
{
mov ax,0x3900
mov ss,ax
mov sp,0x100
Forever:
mov dx,0xf4fd
TstStatus:
in al,dx
testal,0x20
je TstStatus
// Code below is same as _SetEXRegByte(TransmitPortAddr,’X’)
mov ax,’X’
mov dx,0xf4f8
out dx, al
jmp Forever
}
}
/*********************** Function SerialWriteStr **************************
Parameters:
Unit Unit number of the serial port. 0 for SIO port 0, 1 for SIO
port 1.
*str Character string to be written out the serial port.
Returns:
None
Assumptions:
None
Real/Protected Mode
------------------------------------------------------------------------*/
void SerialWriteStr(int Unit, const char far *str)
{
WORD TransmitPortAddr;
WORD StatusPortAddr;
// Set Port base, based on serial port used
TransmitPortAddr = (Unit ? TBR1 : TBR0);
StatusPortAddr = (Unit ? LSR1 : LSR0);
for( ; *str != ‘\0’; str++)
{
// Wait until buffer is empty
while(!(_GetEXRegByte(StatusPortAddr) & SIO_TX_BUF_EMPTY)) ;
// Write Character
_SetEXRegByte(TransmitPortAddr,*str);
}

Intel 386 Specifications

General

Architecture	x86
Clock Speed	12 MHz to 40 MHz
Transistor Count	275, 000
Data Bus Width	32-bit
Address Bus Width	32-bit
Instruction Set	x86
Introduced	1985
Maximum Memory	4 GB
Operating Modes	Real mode, Protected mode, Virtual 8086 mode
MMU	Yes
Voltage	5V
Model	Intel 386
Package	PGA
Process	1.5 μm to 1 μm