II-7
1.3.2
ASIC
<HL-720>
The ASIC is composed of Cell Based IC and has the following function blocks.
(1) Oscillator circuit
Oscillator circuit drives the outside ceramic resonator, and generates the
main clock for the CPU core by dividing the source clock frequency into two.
It is also equipped with the several clocks for timer unit, engine control I/O
unit, CDCC parallel I/O unit, data extension unit and FIFO.
(2) Program ROM
The program ROM of 16 Kbytes is contained in this ASIC.
(3) Working S-RAM
The working S-RAM of 512 Bytes is also contained in this ASIC as a work RAM for
the CPU core.
(4) DRAM control circuit
This circuit generates the RAS, CAS, WE, OE and MA signals for the DRAM and
controls the refresh for the DRAM (CAS before RAS self-refreshing method). The
CPU core, the CDCC parallel I/O unit and the data extension unit access
the DRAM through the DRAM bus controlled by the DRAM control unit.
(5) Interrupt control
This circuit controls all the interrupts to the CPU core. The CPU core has no
priority to each interrupt element. If the first interrupt is accepted, then the second
waits until the first has been complete. The interrupt elements can be masked
respectively.
(6) Timers
The following timers are incorporated:
Timer 1
16-bit timer
Timer 2
10-bit timer
Timer 3
Watch-dog timer
Summary of Contents for HL-720
Page 1: ...SERVICE MANUAL MODEL HL 720 730 730Plus R LASER PRINTER ...
Page 36: ...II 19 1 3 10 Engine I O HL 720 Fig 2 21 shows the engine interface circuit Fig 2 21 ...
Page 37: ...II 20 HL 730 730Plus Fig 2 22 shows the engine interface circuit Fig 2 22 ...
Page 61: ... Fig 3 18 2 4 1 1 1 ...
Page 92: ...SERVICE MANUAL MODEL HL 760 R LASER PRINTER ...
Page 109: ...II 8 1 3 4 DRAM Two 4M bit DRAMs x 16bits are used as the RAM Fig 2 6 ...
Page 113: ...II 12 1 3 10 Engine I O Fig 2 12 shows the engine interface circuit Fig 2 12 ...
Page 114: ...II 13 1 3 11 Paper Feed Motor Drive Circuit Fig 2 13 ...
Page 133: ...Appendix 2 Main PCB Circuit Diagram 1 3 CODE UK3227000 B48K272CIR 1 3 NAME ...
Page 134: ...Appendix 3 Main PCB Circuit Diagram 2 3 CODE UK3227000 B48K272CIR 2 3 NAME ...
Page 135: ...CODE UK3227000 B48K272CIR 3 3 NAME Appendix 4 Main PCB Circuit Diagram 3 3 ...
