w83977atg Winbond Electronics Corp America, w83977atg Datasheet - Page 94

• Manufacturer Part Number: w83977atg
• Description: W83877tf Plus Kbc, Gp I/o, Wake-up, Fir, Cir, Pb-free
• Manufacturer: Winbond Electronics Corp America

8.2.3
The system microprocessor can read the contents of the printer control latch by reading the printer
control swapper. Bit definitions are as follows:
Bit 7, 6: These two bits are a logic one during a read. They can be written.
Bit 5: Direction control bit
Bit 4: A 1 in this position allows an interrupt to occur when ACK changes from low to high.
Bit 3: A 1 in this bit position selects the printer.
Bit 2: A 0 starts the printer (50 microsecond pulse, minimum).
Bit 1: A 1 causes the printer to line-feed after a line is printed.
Bit 0: A 0.5 microsecond minimum high active pulse clocks data into the printer. Valid data must be
8.2.4
The address port is available only in EPP mode. Bit definitions are as follows:
The contents of DB0-DB7 are buffered (non-inverting) and output to ports PD0-PD7 during a write
operation. The leading edge of IOW
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.
When this bit is a logic 1, the parallel port is in input mode (read); when it is a logic 0, the
parallel port is in output mode (write). This bit can be read and written. In SPP mode, this bit is
invalid and fixed at zero.
present for a minimum of 0.5 microseconds before and after the strobe pulse.
Printer Control Latch and Printer Control Swapper
EPP Address Port
1
7
7
6
1
6
5
c
auses an EPP address write cycle to be performed, and the
5
4
3
4
- 86 -
2
3
1
2
W83977ATF/W83977ATG
0
1
STROBE
AUTO FD
INIT
SLCT IN
IRQ ENABLE
DIR
0
PD0
PD1
PD2
PD3
PD4
PD5
PD6
PD7