The readIntrThreshold can be determined by setting the direction bit to 1 and filling the empty tFIFO a byte
at a time until serviceIntr is set. This may generate a spurious interrupt, but will indicate that the threshold
has been reached.
Data bytes are always read from the head of tFIFO regardless of the value of the direction bit. For example
if 44h, 33h, 22h is written to the FIFO, then reading the tFIFO will return 44h, 33h, 22h in the same order
as was written.
cnfgA (Configuration Register A)
ADDRESS OFFSET = 400H
Mode = 111
This register is a read only register. When read, 10H is returned. This indicates to the system that this is
an 8-bit implementation. (PWord = 1 byte)
cnfgB (Configuration Register B)
ADDRESS OFFSET = 401H
Mode = 111
BIT 7 compress
This bit is read only. During a read it is a low level. This means that this chip does not support hardware
RLE compression. It does support hardware de-compression.
BIT 6 intrValue
Returns the value of the interrupt to determine possible conflicts.
BITS [5:3] Parallel Port IRQ (read-only)
Refer to Table 44B.
BITS [2:0] Parallel Port DMA (read-only)
Refer to Table 44C.
ecr (Extended Control Register)
ADDRESS OFFSET = 402H
Mode = all
This register controls the extended ECP parallel port functions.
BITS 7,6,5
These bits are Read/Write and select the Mode.
BIT 4 nErrIntrEn
Read/Write (Valid only in ECP Mode)
1: Disables the interrupt generated on the asserting edge of nFault.
0: Enables an interrupt pulse on the high to low edge of nFault. Note that an interrupt will be generated if
nFault is asserted (interrupting) and this bit is written from a 1 to a 0. This prevents interrupts from
being lost in the time between the read of the ecr and the write of the ecr.
BIT 3 dmaEn
Read/Write
1: Enables DMA (DMA starts when serviceIntr is 0).
0: Disables DMA unconditionally.
BIT 2 serviceIntr
Read/Write
1: Disables DMA and all of the service interrupts.
0: Enables one of the following 3 cases of interrupts. Once one of the 3 service interrupts has occurred
serviceIntr bit shall be set to a 1 by hardware. It must be reset to 0 to re-enable the interrupts. Writing
this bit to a 1 will not cause an interrupt.
case dmaEn=1:
During DMA (this bit is set to a 1 when terminal count is reached).
case dmaEn=0 direction=0:
This bit shall be set to 1 whenever there are writeIntrThreshold or more bytes free in the FIFO.
case dmaEn=0 direction=1:
SMSC LPC47B27x
- 85 -
Rev. 08-10-04
DATASHEET
SMSC [ SMSC CORPORATION ]
