Memory access interface for a micro-controller system with address/data multiplexing bus
A memory access interface for connecting a memory to a micro-controller having an address/data multiplexing bus and a microprocessor is proposed. The memory access interface includes an address latch, a multiplexer, and a data buffer. The address latch latches and outputs the lower-bit address signal on the address/data multiplexing bus of the micro-controller when an address-latch-enable signal is enabled. The multiplexer receives the lower-bit address signal latched by the address latch, a higher-bit address signal outputted from the micro-controller, and an address signal outputted from the microprocessor and selectively outputs the address signal of the micro-controller or the address signal of the microprocessor as the address signal of the memory according to a first control signal. The data buffer transmits the signal of the data bus of the memory to the address/data multiplexing bus of the micro-controller during a data cycle of the micro-controller, and maintains a high impedance state during an address cycle of the micro-controller.
1. A memory access interface for connecting a memory to a micro-controller and a first circuitry, the micro-controller being capable of transmitting a first group address signals and a second group address signals, the micro-controller being capable of transmitting the first group address signals or accessing data signals via an address/data bus, the memory access interface comprising:
an address holder for receiving the first group address signals on the address/data multiplexing bus and a first enable signal outputted from the micro-controller, and outputting the first group address signals when the first enable signal is enabled; and
a multiplexer for receiving the first group address signals outputted from the address holder, the second group address signals outputted from the micro-controller, and third address signals outputted from the first circuitry, the multiplexer being controlled by a first control signal of the micro-controller for selectively outputting the first and second group address signals or outputting the third address signals to the memory;
wherein the micro-controller and the first circuitry can access the data of the memory according to the first enable signal.
2. The memory access interface according to claim 1 , wherein the first control signal is the first enable signal.
3. The memory access interface according to claim 1 , wherein the first control signal is a reading signal of the micro-controller.
4. The memory access interface according to claim 1 , wherein the micro-controller accesses the data of the memory during a data cycle of the micro-controller and the first circuitry accesses the data of the memory during an address cycle of the micro-controller.
5. The memory access interface according to claim 1 , wherein the first circuitry comprises a microprocessor.
6. The memory access interface according to claim 1 , wherein the address holder is an address latch and the first control signal is an address-latch-enable signal.
7. The memory access interface according to claim 1 , wherein the first group address signals are the lower-bit address signals of the micro-controller, and the second group address signals are the higher-bit address signals of the micro-controller.
8. The memory access interface according to claim 1 , further comprising a data buffer for transmitting the data signals from the memory to the address/data bus of the micro-controller during the data cycle of the micro-controller, and for maintaining a high impedance state during the address cycle of the micro-controller, the data buffer being controlled by a second control signal of the micro-controller.
9. The memory access interface according to claim 8 , wherein the second control signal is the first enable signal.
10. A memory access method for controlling the access among a memory, a micro-controller with an address/data multiplexing bus and a first device, the memory access method comprising the steps of:
the micro-controller outputting a first address signal during an address cycle of the micro-controller;
latching the first address signal as a latched address signal;
the first device outputting a second address signal to the memory and reading/writing data from/to the memory during the address cycle of the micro-controller; and
outputting the latched address signal to the memory during a data cycle of the micro-controller; and
the micro-controller reading/writing data from/to the memory during the data cycle of the micro-controller.
11. The memory access method according to claim 10 , wherein the micro-controller further outputs a third address signal to the memory during the data cycle.