Tektronix PHASER 380, Service Manual

Page: 105 / 346

Service Manual 5-3
Theory of Operation
5
Printer electronics
■
Main board
■
Power control board
■
I/O boards (3)
■
Network card
■
Power supply
Main board
The main board performs two functions: it controls the actions of the print
engine and it performs the PostScript interpreting of the host’s data file into a
bitmap format to be printed by the print engine. To accomplish this, the main
board features two processors and their associated support electronics.
The PostScript interpreter is based around a 29030 processor. The PostScript
software and 29030 self-tests are stored in ROM. Communication with host
computers is routed through I/O ASICs to the 29030 data bus.
The print engine controller is based on a 68330 processor. The print engine
firmware and 68330 self tests are stored in ROM. Stored engine parameters are
saved in EEPROM.
A digital motion control (DMC) ASIC controls the I
2
C (Inter-Integrated Circuit)
bus, which links all the printer sensors, solenoids, clutches motors, heaters and
the front panel to the main board. The I
2
C bus is an independent address/data
bus interconnecting all the I/O boards. Each I/O board features an address
decoder and data buffer which respond to the DMC. The DMC writes to a
particular I/O board, for example, for that board’s sensor states and then reads
that board’s data buffer for the requested sensor data. Similarly, it writes to a
particular I/O board to activate its solenoids.
Communication between the two processors is accomplished through an
inter-processor controller (IPC) which is basically a byte-wide, bi-directional
buffer. Data from one processor, presented to the buffer, flags the other
processor to read the data and return data, if necessary.