Zebra 01407-000 Manual Do Utilizador
Interfaces
Parallel Interface (TTP 1020)
Parallel Interface (TTP 1020)
70
P1003643-001
TTP 1020™/TTP 1030™ Technical Manual
03/03/2009
The signal timing follows the IEEE-1284 parallel printer interface specification.
The ECP port also has the advantage of using DMA channels and FIFO buffers so that data
can be shifted around without using I/O instructions.
can be shifted around without using I/O instructions.
Negotiation
Peripherals are not required to implement all of the modes (Nibble Mode and EPP Mode are
implemented in TTP 1020). Because of this, the host platform needs a method to determine
what mode the attached peripheral supports, and to have a controlled method to set the
interface to one of the supported modes.
implemented in TTP 1020). Because of this, the host platform needs a method to determine
what mode the attached peripheral supports, and to have a controlled method to set the
interface to one of the supported modes.
The concept of negotiation was developed to fill this need. Negotiation is a sequence of events
on the parallel port interface that would not effect an older device but would provide
identification of a 1284 peripheral. An older device will not respond to the negotiation
sequence. Therefore the host would remain in Compatibility Mode. A IEEE-1284 peripheral
responds to the sequence, and could then be set to any of the modes supported by both
peripheral and host.
on the parallel port interface that would not effect an older device but would provide
identification of a 1284 peripheral. An older device will not respond to the negotiation
sequence. Therefore the host would remain in Compatibility Mode. A IEEE-1284 peripheral
responds to the sequence, and could then be set to any of the modes supported by both
peripheral and host.
During the negotiation phase, the host places a request on the data lines and then initiates the
negotiation sequence. The request can be to put the interface into a particular mode, or request
a device ID from the peripheral.
negotiation sequence. The request can be to put the interface into a particular mode, or request
a device ID from the peripheral.
shows the
basic negotiation sequence.
A byte called the extensibility byte is used during negotiation to request that. The peripheral
enters a specific transfer mode, or to request that the peripheral sends a device ID. This ID will
allow the host to identify the type of attached peripheral. The device ID can be returned in any
reverse channel mode other than EPP.
enters a specific transfer mode, or to request that the peripheral sends a device ID. This ID will
allow the host to identify the type of attached peripheral. The device ID can be returned in any
reverse channel mode other than EPP.
describes the extensibility byte and
allowed values.