
Hardware Description
MFC 2000 Multifunctional Peripheral Controller 2000
100723A
Conexant
17-5
PDOE
Parallel Data Output Enable
This bit performs two functions. It controls the state of the PD bus
three-state output drives, and it qualifies the latching of data from the
PD bus into the Parallel Port Data Register. When set, PDOE enables
the PD bus output pin drivers, and prevents data from being latched
into the Parallel Port Register.
Setting ABRT affects the operation of PDOE. IF ABRT is set,
SLCTINn (1284ACTIVE) must remain high to allow PDOE to be set or
remain set. If ABRT is set and SLCTINn (1284Active) goes low, PDOE
is cleared, and setting PDOE has no effect.
ABRT
Abort
This causes the PPI to use SLCTINn (1284Active) to detect when the
host suddenly aborts a reverse transfer and returns to compatibility
mode. If ABRT is set, a low level on SLCTINn (1284 Active) causes
PDOE to be cleared and the PD bus output drivers to be three-stated.
In fact, if ABRT is set and SLCTINn (1284Active) is low, setting PDOE
has no effect. This protection logic, as all internal logic, operates from
a synchronized and optionally digitally filtered SLCTINn (1284Active)
that is latched into the parallel Port Interface Register.
This is a read-only status bit which indicates when run-length
decompression is taking place during ECP forward data transfers.
RLD is set when a run-length count is received and loaded into the
internal counter, and cleared when the last read of the Parallel Port
Data Register takes place. This bit can only be set when ECP with
RLE (mode 3) is enabled. If MODE is reprogrammed during a
decompression, decompression continues and RLD remains set until
the operation is completed. RLD is cleared when RST is issued.
This is a read-only status bit that indicates when parallel port data
from the host is latched in the Parallel Port Data Register. FFULL is
cleared when the Parallel Port Data Register is read. When
handshaking and DMA is enabled, FFULL sets and clears as data is
latched and read during forward data transfers. FFULL is also cleared
when RST is issued.
This is a read-only status bits indicates when parallel port data to the
host is latched in the Parallel Port Data Register. RFULL is cleared
when the Parallel Port Data Register is sent. When handshaking and
DMA is enabled, RFULL sets and clears as data is latched and sent
during reverse data transfers. RFULL is also cleared when RST is
issued.
Active low resets all the state machines and is programmable using
this register bit. During the normal operation this bit needs to be set to
allow the state machine to start.
Active low to enable tri-state input during the forward(PC to printer)
transfers.
RLD
Run Length Decompression
FFULL
Forward Data Register Full
RFULL
Reverse Data Register Full
PPIRSTN
Parallel port software reset
TRIZN
Tri-state output enable