
W83977EF/ CTF
PRELIMINARY
Publication Release Date: March 1999
-67 -
Revision A1
The contents of DB0-DB7 are buffered (non-inverting) and output to ports PD0-PD7 during a write
operation. The leading edge of IOW#
c
auses an EPP address write cycle to be performed, and the
trailing edge of IOW#
latches the data for the duration of the EPP write cycle.
PD0-PD7 ports are read during a read operation. The leading edge of IOR#
causes an EPP address
read cycle to be performed and the data to be output to the host CPU.
5.2.5 EPP Data Port 0-3
These four registers are available only in EPP mode. Bit definitions of each data port are as follows:
1
2
3
4
5
6
7
0
PD0
PD1
PD2
PD3
PD4
PD5
PD6
PD7
When accesses are made to any EPP data port, the contents of DB0-DB7 are buffered (non-
inverting) and output to the ports PD0-PD7 during a write operation. The leading edge of IOW#
causes an EPP data write cycle to be performed, and the trailing edge of IOW#
latches the data for
the duration of the EPP write cycle.
During a read operation, ports PD0-PD7 are read, and the leading edge of
IOR#
causes an EPP read
cycle to be performed and the data to be output to the host CPU.
5.2.6 Bit Map of Parallel Port and EPP Registers
REGISTER
7
6
5
4
3
2
1
0
Data Port (R/W)
PD7
PD6
PD5
PD4
PD3
PD2
PD1
PD0
Status Buffer (Read)
BUSY#
ACK#
PE
SLCT
ERROR#
1
1
TMOUT
Control Swapper (Read)
1
1
1
IRQEN
SLIN
INIT#
AUTOFD#
STROBE#
Control Latch (Write)
1
1
DIR
IRQ
SLIN
INIT#
AUTOFD#
STROBE#
EPP Address Port R/W)
PD7
PD6
PD5
PD4
PD3
PD2
PD1
PD0
EPP Data Port 0 (R/W)
PD7
PD6
PD5
PD4
PD3
PD2
PD1
PD0
EPP Data Port 1 (R/W)
PD7
PD6
PD5
PD4
PD3
PD2
PD1
PD0
EPP Data Port 2 (R/W)
PD7
PD6
PD5
PD4
PD3
PD2
PD1
PD0
EPP Data Port 3 (R/W)
PD7
PD6
PD5
PD4
PD3
PD2
PD1
PD0