INT 14 - X00 FOSSIL - EXTENDED SERIAL PORT STATUS/CONTROL
AH = 1Fh
AL = 00h read modem control register
Return: BL = modem control register (see below)
AH = status
AL = 01h write modem control register
BL = modem control register
bit 0: data terminal ready
bit 1: request to send
bit 2: OUT1
bit 3: OUT2 (interrupts) enabled
bit 4: LOOP
bits 5-7 reserved
Return: AX = status
DX = port number
SeeAlso: AH=05h"SERIAL I/O"
Notes:  this function is intended to exactly emulate the PS/2 BIOS AH=05h call
X00 forces BL bit 3 set (interrupts cannot be disabled)

See also: 1400

141F - X00 FOSSIL - EXTENDED SERIAL PORT STATUS/CONTROL