
6. 
SMSC DS – LPC47M192 
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DATASHEET 
a) The chip deasserts nDATASTB or nADDRSTRB, this marks the beginning of the termination phase.  If it has 
not already done so, the peripheral should latch the information byte now. 
b) The chip latches the data from the internal data bus for the PData bus and drives the sync that indicates that no 
more wait states are required followed by the TAR to complete the write cycle. 
Peripheral asserts nWAIT, indicating to the host that any hold time requirements have been satisfied and 
acknowledging the termination of the cycle. 
Chip may modify nWRITE and nPDATA in preparation for the next cycle. 
7. 
8. 
EPP 1.9 Read 
The timing for a read operation (data) is shown in timing diagram EPP Read Data cycle. The chip inserts wait states 
into the LPC I/O read cycle until it has been determined that the read cycle can complete.  The read cycle can 
complete under the following circumstances: 
1. If the EPP bus is not ready (nWAIT is active low) when nDATASTB goes active then the read can 
complete when nWAIT goes inactive high. 
2. If the EPP bus is ready (nWAIT is inactive high) then the chip must wait for it to go active low before 
changing the state of nWRITE or before nDATASTB goes active.  The read can complete once nWAIT 
is determined inactive. 
Read Sequence of Operation 
1. 
The host initiates an I/O read cycle to the selected EPP register. 
2. 
If WAIT is not asserted, the chip must wait until WAIT is asserted. 
3. 
The chip tri-states the PData bus and deasserts nWRITE.   
4. 
Chip asserts nDATASTB or nADDRSTRB indicating that PData bus is tri-stated, PDIR is set and the nWRITE signal 
is valid. 
5. 
Peripheral drives PData bus valid. 
6. 
Peripheral deasserts nWAIT, indicating that PData is valid and the chip may begin the termination phase of the 
cycle. 
7.  a) 
The chip latches the data from the PData bus for the internal data bus and deasserts nDATASTB or 
nADDRSTRB. This marks the beginning of the termination phase. 
b) The chip drives the sync that indicates that no more wait states are required and drives valid data onto the 
LAD[3:0] signals, followed by the TAR to complete the read cycle. 
8. 
Peripheral tri-states the PData bus and asserts nWAIT, indicating to the host that the PData bus is tri-stated. 
9. 
Chip may modify nWRITE, PDIR and nPDATA in preparation for the next cycle.  
EPP 1.7 OPERATION 
When the EPP 1.7 mode is selected in the configuration register, the standard and bi-directional modes are also 
available. If no EPP Read, Write or Address cycle is currently executing, then the PDx bus is in the standard or bi-
directional mode, and all output signals (STROBE, AUTOFD, INIT) are as set by the SPP Control Port and direction 
is controlled by PCD of the Control port. 
In EPP mode, the system timing is closely coupled to the EPP timing.  For this reason, a watchdog timer is required 
to prevent system lockup.  The timer indicates if more than 10usec have elapsed from the start of the EPP cycle to 
the end of the cycle.  If a time-out occurs, the current EPP cycle is aborted and the time-out condition is indicated in 
Status bit 0.  
Software Constraints 
Before an EPP cycle is executed, the software must ensure that the control register bits D0, D1 and D3 are set to 
zero.  Also, bit D5 (PCD) is a logic “0” for an EPP write or a logic “1” for and EPP read. 
EPP 1.7 Write 
The timing for a write operation (address or data) is shown in timing diagram EPP 1.7 Write Data or Address cycle.  
The chip inserts wait states into the I/O write cycle when nWAIT is active low during the EPP cycle.  This can be used 
to extend the cycle time.  The write cycle can complete when nWAIT is inactive high. 
Write Sequence of Operation 
1. The host sets PDIR bit in the control register to a logic “0”.  This asserts nWRITE.   
2. The host initiates an I/O write cycle to the selected EPP register. 
3. The chip places address or data on PData bus. 
4. Chip asserts nDATASTB or nADDRSTRB indicating that PData bus contains valid information, and the 
WRITE signal is valid.