Brother HL-720 - B/W Laser Printer Service Manual page 28

(7) CDCC parallel I/O
<Data receiving>
There are two modes in this unit. One is the CPU receiving mode and the other is
the DMA receiving mode. In the CPU receiving mode the CPU receives the
command data from the PC, and after the CPU is switched to the DMA mode, it
receives the image data and writes to the DRAM directly.
CPU Receiving Mode
STROBE
BUSY
ACK
STROBE
BUSY
ACK
BUSY goes HIGH at the falling edge of STROBE. The data (8 bits) from the PC is
latched in the data buffer at the rising edge of STROBE. The pulse width of ACK
differs according to the speed MODE as shown above. BUSY goes LOW at the
rising edge of ACK.
<IEEE1284 support>
This supports the IEEE1284 data transfer with the following mode.
Nibble mode
Byte mode
(8) Data extension
This circuit extents the compressed image data which are received from the PC,
and writes the bit map data to the FIFO.
(9) Software support
Supports 16 x 16 rotation, bit expansion, and bit search.
(10)EEPROM I/O
One output port and one I/O port are assigned.
90 µsec 0.5 µsec
1.5 µsec 0.5 µsec
II-11