CadJet T-200 Service Manual

The gate array contains the hardware logic for dot firing, monitoring changes in the Carriage Assembly position, controlling DMA through the parallel port, receiving commands from the microswitches and generating the PWM (Pulse Width Modulation) waveforms for the servo controller.

The gate array is a Xilinx device. It is a static RAM-based field programmable gate array. This means that the logic that it implements is determined by configuration information in internal RAM storage. Each time power is turned on, this information must be downloaded from the system ROM. This type of gate array allows for the flexibility of upgrading the logic by simply downloading the new system software.

Memory Circuits

Memory is used to retain large amounts of information. This information is stored in the device memory in the form of binary bits.

Printer memory consists of Flash, DRAM, and EEPROM.

Maximum installable memory is as follows:

DRAM = 32 MB

Flash = 1 MB

Serial EEPROM = 1KB


Flash EEPROM is Electrically Erasable, Programmable, Read Only

Memory used to store instructions and data constants which the microprocessor can access and interpret, with no loss of information when power is off.

Theory of Operation 2-7

CadJet T-200 Service Manual

The system firmware is stored in Flash EEPROM. The Flash

EEPROM allows the firmware to be upgraded by downloading the files containing the new firmware. It can be erased and reprogrammed more than 10,000 times. The term “Flash” means that bytes cannot be individually erased. A block or the whole device is erased at the same time and the block or whole device is then reprogrammed.

The normal method of downloading new firmware is to send the unit the files containing the code using either the GO.EXE utility or printing the file to the unit. This requires using an appropriate host utility and can be done through the serial port (for Macintosh users) or the parallel port

(for PC users). See Firmware Downloading in Chapter 3 for the procedures.


DRAM is Dynamic Random Access Memory which provides temporary storage of the microprocessor calculation and input/output data. It is also a faster type of memory then the Flash EEPROM. That’s why the printer control program is also copied from the Flash EEPROM to RAM, where it can be executed faster.

The printer also has one 168-pin 64-bit DIMM socket for a DRAM memory module. The printer is supplied with a 32 Megabyte DIMM installed on the MPWA. The following DIMM sizes are supported:

32MB, 64MB and 128MB.


Serial EEPROM is an Electrically Erasable, Programmable, Read Only

Memory which provides storage for calibration constants and user configuration data entered from the host computer.

An 8K bit serial nonvolatile EEPROM stores calibration and configuration information. It retains data while the unit is off.

Theory of Operation 2-8

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