Chips used in design:
Z80
40 years old famous microprocessor
SST39SF010A
ROM - 128kB flash ROM, 32kB in use only , on-board programmable and erasable
AS6C4008
RAM - 512kB RAM, divided in two banks, 16 virtual pages per bank, 16kB each
74HC253
Memory selector - address space 0-32kB could be switched to ROM or RAM
74HC670
Memory pages mapping - any (virtual) 16kB RAM block could be mapped to any quarter of a memory space
74HC138
Output port selector - selects general output port, two internal output ports and memory bank multiplexer
74HC574
General output port - simple 8 bit port
74HC259
Bit-based output ports - two 8 bit ports, mainly for internal use, each bit independently settable
74HC32 (1G version)
Input port selector - selects general input port or internal multiplexed input port
74HC541
General input port - simple 8 bit input port
74HC251
Multiplexed input port - single-bit-read input port
74LVC07 (2G version), 74LCX125
Level converters - convert logic levels for SD card, PS/2 keyboard or I2C bus
TXC 7C
Oscillator - single package 5V clock generator
Daughter board:
DS1307
Real time clock - date and time
24C64 (24C128, 24C512...)
serial EEPROM, not in use now