NAME
TYPE
DESCRIPTION
nAck
I
Indicates valid data driven by the peripheral when asserted. This signal
handshakes with nAutoFd in reverse.
PeriphAck (Busy)
I
This signal deasserts to indicate that the peripheral can accept data. This
signal handshakes with nStrobe in the forward direction. In the reverse
direction this signal indicates whether the data lines contain ECP
command information or data. The peripheral uses this signal to flow
control in the forward direction. It is an "interlocked" handshake with
nStrobe. PeriphAck also provides command information in the reverse
direction.
PError
I
Used to acknowledge a change in the direction the transfer (asserted =
(nAckReverse)
forward).
The peripheral drives this signal low to acknowledge
nReverseRequest. It is an "interlocked" handshake with nReverseRequest.
The host relies upon nAckReverse to determine when it is permitted to
drive the data bus.
Select
nAutoFd
(HostAck)
I
O
Indicates printer on line.
Requests a byte of data from the peripheral when asserted, handshaking
with nAck in the reverse direction. In the forward direction this signal
indicates whether the data lines contain ECP address or data. The host
drives this signal to flow control in the reverse direction. It is an
"interlocked" handshake with nAck. HostAck also provides command
information in the forward phase.
Generates an error interrupt when asserted. This signal provides a
mechanism for peer-to-peer communication. This signal is valid only in the
forward direction. During ECP Mode the peripheral is permitted (but not
required) to drive this pin low to request a reverse transfer. The request is
merely a "hint" to the host; the host has ultimate control over the transfer
direction. This signal would be typically used to generate an interrupt to
the host CPU.
nFault
I
(nPeriphRequest)
nInit
O
O
Sets the transfer direction (asserted = reverse, deasserted = forward).
This pin is driven low to place the channel in the reverse direction. The
peripheral is only allowed to drive the bi-directional data bus while in ECP
Mode and HostAck is low and nSelectIn is high.
nSelectIn
Always deasserted in ECP mode.
Register Definitions
The register definitions are based on the standard IBM addresses for LPT. All of the standard printer ports
are supported. The additional registers attach to an upper bit decode of the standard LPT port definition to
avoid conflict with standard ISA devices. The port is equivalent to a generic parallel port interface and may
be operated in that mode. The port registers vary depending on the mode field in the ecr. The table below
lists these dependencies. Operation of the devices in modes other that those specified is undefined.
Table 42 - ECP Register Definitions
NAME
ADDRESS (Note 1)
+000h R/W
+000h R/W
+001h R/W
+002h R/W
+400h R/W
+400h R/W
+400h R/W
+400h R
ECP MODES
FUNCTION
data
000-001
011
All
Data Register
ecpAFifo
dsr
ECP FIFO (Address)
Status Register
dcr
All
Control Register
cFifo
ecpDFifo
tFifo
cnfgA
cnfgB
ecr
010
011
110
111
111
All
Parallel Port Data FIFO
ECP FIFO (DATA)
Test FIFO
Configuration Register A
Configuration Register B
Extended Control Register
+401h R/W
+402h R/W
Note 1: These addresses are added to the parallel port base address as selected by configuration
register or jumpers.
Note 2: All addresses are qualified with AEN. Refer to the AEN pin definition.
SMSC LPC47B27x
- 82 -
Rev. 08-10-04
DATASHEET
SMSC [ SMSC CORPORATION ]
