Asic - Brother HL-1020 Service Manual

1.3.2

ASIC

HL-820/1020/1040
The ASIC is composed of a Cell Based IC that contains the following functional blocks.
(1) Oscillator circuit
Generates the main clock for the CPU by dividing the source clock frequency into
two.
(2) Address decoder
Generates the CS for each device.
(3) DRAM control
Generates the RAS, CAS, WE, OE and MA signals for the DRAM and controls
refresh processing (CAS before RAS self-refreshing method).
(4) Interrupt control
Interrupt levels:
Priority
(5) Timers
The following timers are incorporated:
Timer 1
Timer 2
Timer 3
(6) FIFO
A 5,120-bit FIFO is incorporated. Data for one raster scan is transferred from the
RAM to the FIFO by DMA transmission and is output as serial video data. The
data cycle is 10.22 MHz.
(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.
High 7 NMI
6 FIFO
5 EXINT(Option Serial I/O)
4 BD / Timer 1
3 SCANINT
2 CDCC / BOISE / DATA EXTENSION
Low 1 Timer 2
16-bit timer
10-bit timer
Watch-dog timer
II-9