Oki MICROLINE 390 Maintenance Manual

Also see for Microline 390: Handbook Product update Service manual User guide Product update

(6) EEPROM (Q9)This 256-bit serial data electrically erasable and programmable ROM stores the menu modedata.(7) LSI (MSM79H097) (46)The MSM79H097 controls the DMA, head drive and LF microstep. The details are describedbelow.(a) DMA controlData transfers from ROM to D-RAM or between D-RAMS is performed by DMA transfereliminating the need of the CPU to perform such operations.By setting the address of the transfer origin, the transfer destination and the number ofbytes to be transferred and starting from the CPU, data in memory can be transferreddirectly.(b) Head drive controlDrive pulses are produced for impact timing of the head using IPT signals as triggers. IPTsignals are generated by phase A and B signals from the spacing motor.The pulse width of this drive differs according to the number of the impact pins. Its durationcan be preset by the CPU.(c) Print data transfer controlPerforms the serial transfer control of print data.Print data will be transferred automatically from the memory area stored for decoding tothe register in this LSI in synchronization with an IPT signal coming from MSM6990.The data which is stored in the register will be transferred to the head drive unit as serialdata just before the next impact timing.(d) LF micro step controlPerforms micro step control to enable fine feed of the LF motor.(e) Memory interfaceThis function expands the memory space for ROMs and RAMS which are connected to thisLSI, and makes it possible for the memory to access 368 Kbytes.(0 D-RAM refreshPerforms refreshing of D-RAMS using the CAS before RAS refresh method.3-3