I/O Controller
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From: Computer Freak on 27 Dec 2005 10:01 On a typical microprocessor, a distinct I/O address is used to refer to the I/O data registers and a distinct address for the control and status registers in an I/O controller for a given device. Such registers are refered to as ports. In intel 8088, two I/O instruction formats are used. In one format, the 8-bit opcode specifies an dI/O operation; this is followed by an 8-bit port address. Other I/O opcodes imply that the port address is in the 16-bit DX register. How many ports can the 8088 address in each I/O addressing mode??? Thank you!
From: Eric P. on 27 Dec 2005 11:14 Computer Freak wrote: > > On a typical microprocessor, a distinct I/O address is used to refer to > the I/O data registers and a distinct address for the control and > status registers in an I/O controller for a given device. Such > registers are refered to as ports. In intel 8088, two I/O instruction > formats are used. In one format, the 8-bit opcode specifies an dI/O > operation; this is followed by an 8-bit port address. Other I/O opcodes > imply that the port address is in the 16-bit DX register. How many > ports can the 8088 address in each I/O addressing mode??? > Thank you! If it is a serial port, then obviously just one at a time. However on a parallel port, it can control up to 7 or 15 devices simultaneously (device 0 is reserved as the cpu id). Eric
From: Del Cecchi on 27 Dec 2005 19:44 "Computer Freak" <nivine.dalleh(a)gmail.com> wrote in message news:1135692298.276122.236080(a)g49g2000cwa.googlegroups.com... > On a typical microprocessor, a distinct I/O address is used to refer to > the I/O data registers and a distinct address for the control and > status registers in an I/O controller for a given device. Such > registers are refered to as ports. In intel 8088, two I/O instruction > formats are used. In one format, the 8-bit opcode specifies an dI/O > operation; this is followed by an 8-bit port address. Other I/O opcodes > imply that the port address is in the 16-bit DX register. How many > ports can the 8088 address in each I/O addressing mode??? > Thank you! > In the former case, the processor can address 8 ports, one for each bit. The ports are enabled by setting a bit corresponding to the port. In the second case, which works much the same, 64 ports can be addressed. The first byte on the bus selects one of eight groups of eight ports. The second byte selects the port within the group. del cecchi
From: Peter Dickerson on 29 Dec 2005 06:09 "Computer Freak" <nivine.dalleh(a)gmail.com> wrote in message news:1135692298.276122.236080(a)g49g2000cwa.googlegroups.com... > On a typical microprocessor, a distinct I/O address is used to refer to > the I/O data registers and a distinct address for the control and > status registers in an I/O controller for a given device. Such > registers are refered to as ports. In intel 8088, two I/O instruction > formats are used. In one format, the 8-bit opcode specifies an dI/O > operation; this is followed by an 8-bit port address. Other I/O opcodes > imply that the port address is in the 16-bit DX register. How many > ports can the 8088 address in each I/O addressing mode??? > Thank you! This is a trick question. Obviously each addressing mode addresses one port. P
From: cat12 on 30 Dec 2005 04:14 Hi I am doing a course for the A+ computer maintenance at college which that does answer my question
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