Index wersja polska wersja polska

Elektronika MK-90 - hardware

LCD controller КА1835ВГ3

This chip transfers display data from the RAM to the LCD drivers КА1835ИД1. Additionally it serves as a memory controller.

$E800 - address register, word size
This register specifies the starting address of the display memory.
$E802 - control register (?), word size
This register of unknown function is initialised with a fixed value $88C6.

Serial bus controller КА1835ВГ4

The controller supports eight serial channels, out of which four are used in the MK-90. All devices hooked to the bus share common DATA and SELECT lines, but receive separate CLK signals.

Channel 0 and 1 are used by the SMP memory modules.
Channel 2 is used by the keyboard controller КА1835ВГ1.
The CLK output of the channel 3 drives the piezo buzzer.

$E810 - data register, byte size
This register is used to transfer data from/to the SMP memory modules.
$E812 - transfer rate register, word size
This register specifies the frequency of the CLK signal.
frequency = 800kHz / register_value
$E814 - control and status register, byte size
Function of individual bits:
bits 2-0 select the serial channel
bit 3 specifies the transfer direction: 0=read, 1=write
bit 7 is set when the transfer is completed and the controller is ready for next data
$E816 - command register, byte size
Writing to this register transfers commands to the SMP memory module. Reading from this register returns the keyboard scan code (row and column of a pressed key). Additionally pressing a key causes a VIRQ interrupt request to the vector at address $00C8.

Real time clock КА512ВИ1

It's a direct equivalent of the of the MC146818 real time clock. A 32768Hz crystal oscillator is used as the time base. The Square Wave Output SQW drives the EVNT interrupt input with a frequency of 32Hz.

The chip bus lines AD0-AD7 are connected to the system bus lines AD1-AD8. Therefore any data written to the chip have to be shifted left by one bit, and any data read from the chip have to be shifted right by one bit. Also the chip registers are selected by consecutive even addresses.

The chip occupies the address range $EA00-$EA7E.