mcs7717 MosChip, mcs7717 Datasheet - Page 31

• Manufacturer Part Number: mcs7717
• Description: Three Port Usb Hub With 1 Serial, 1 Printer
• Manufacturer: MosChip

Rev. 1.7
Mode Changes
After a hardware reset Nibble Mode is selected as the default mode. It is required to select mode 000 or 001
before any other mode configuration.
Mode “000”
SPP/Centronics/Compatible Mode
Forward direction only. The direction bit is forced to “0” and PD7-PD0 are set to the output direction. The
Parallel Port is under software control. This mode defines the protocol used by most PCs to transfer data to
a printer. It is commonly called the “Centronics” mode and is the method utilized with the Standard Parallel
Printer port. Data is placed on the PD7-PD0 ports, and the printer status is checked via the DSR register.
If no error condition is flagged and the printer is not busy, software toggles the nSTROBE pin to latch the
PD7-PD0 data into the printer. This operating cycle continues when the printer/peripheral issues the data
acknowledge signal (pulses the ACK and nBUSY pins).
Mode “001”
Nibble Mode
The Nibble Mode is the most common way to get reverse channel data from the printer or peripheral.
This mode is usually combined with the SPP Mode or a proprietary forward channel mode to create a Bi-
Directional channel. In this mode printer status bits are used as Nibble bits.
Mode “010”
FIFO Output Mode
In this mode, Bytes written to the FIFO are transmitted automatically using the SPP/Centronics standard
protocol.
Bit Order for Nibble Mode
nFAULT
nFAULT
BUSY
BUSY
SLCT
SLCT
Pin
PE
PE
Three Port USB Hub with 1 Serial, 1 Printer
Data Bit
Bit-7
Bit-6
Bit-5
Bit-4
Bit-3
Bit-2
Bit-1
Bit-0
MCS7717
Page 31