Figure 1-23. Seima Board - Epson SQ-B50/2550 Technical Manual

REV.-A
1.5.3 SEIMA Board
The SEIMA board is the main board in the printer, and contains a logic control circuit and an analog
circuit. The parallel interface connector for the host computer, the connector for the externa! font/PROM
cartridge, and the connector for other units are also included.
The HD64180 CPU (1 OC) is used, and the following memories and gate arrays are assigned in the
262K-byte external address space.
• Memories
512K-byte CPU program ROM : 128
4M-byte C.G. (Character Generator) : 108
256K-byte PSRAM : 118
256K-byte SRAM : 13C
• Gate arrays
Parallel Interface (PIF) : 12C
Memory Management Unit (MMU) :88
Printhead Controller (PHC) :68
DC Motor Control Unit (DCU) :48
Motor Control Unit (MCU) :2A
The logic circuits are composed of the above ICs.
The analog circuits consist of the circuits for each mechanism, a buzzer circuit, and a battery circuit.
A lithium battery in the battery circuit backs up the head cleaning timer, in addition to the SRAM (13C)
which stores the values set in the SelecType mode, while the printer power is off. The lithium battery
requires no maintenance.
Figure 1-23. SEIMA Board
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