Extended memory circuit diagram design

Industrial Router Crystal 3.2*2.5mm 3225 26M (26.000MHZ) 12PF 10PPM 20PPM 30PPM

Photocoupler

The STC89C516RD microcontroller contains 1280 bytes of RAM data memory, which is sufficient for general applications. However, because the RTOS real-time multitasking operating system in the system needs to occupy a part of RAM, a large amount of data needs to be stored, and the LCD display interface also needs to occupy RAM. Space, so choose to expand the 32K bytes of RAM data memory. The expanded data memory is done by CY62256.

CY62256 is a 32KX8-bit static random access memory chip. A0~A14 are on-chip 15-bit address lines, I/0 ports are 8-bit bidirectional data lines, CE is a chip select signal (active low), and 0E is a read enable signal line. (Active low), WE is the write signal line (active low). CY62256 chip select signal CE is connected to the A15 bit of the microcontroller, CY62256 is 32K (215) capacity RAM occupies 15 address lines. According to such a connection, the decoding address of CY62256 is 0000H, EFFFH, and a total of 32K. The 74HC373 in Figure 3.6 is the address latch. His role is to separate and latch the address signals in the address/data bus time division multiplexing port of the microcontroller for use in the extended data memory or program memory (the system does not have extended program memory). The ALE of the microcontroller is the low 8-bit address latch control signal, which is connected to the LE pin of the 74HC373, enabling the 373 to latch the address signal.