Replacing a CY7C14X slave device with a CY7C13X master device

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    Question: For a Dual port SRAM, Can I replace a slave device with a master device? What are the differences between the slave devices and master devices? - Can I use only master devices?



    Initially, Cypress DP-SRAMs were manufactured separetely as master and slave device.  The viability of replacing a dual-port slave with a dual-port master depends on the application. The only difference between the devices is the operation of the BUSY pin found on each port. On the master devices, the BUSY pins are open drain outputs. Busy is driven low if a port tries to access an address already being accessed by the other port. Only one port will drive BUSY low at any given time. If BUSY is found to be low on a port, that port is blocked from writing the address. On the slave devices, BUSY is an input to be accepted from the master device. If the BUSY input of a port on the slave device is low, then that port will be blocked from writing the current address. Since there is only one master device driving the 2 BUSY signals, all the devices stay in sync regarding which port has control over an address in contention. If multiple master devices are used in width expansion, then each device will make its own determination which port is given control. This can leave to a hang up where one device choses the left port as the winner and one device chooses the right port as a winner. This situation should be avoided as much as possible. If the design of the application guarentees that both ports cannot access the same address, then substituting 136 devices for 146 devices should work okay. However, if it is a possibility that both ports will simultaneously access the same address, then there should only be one single master device and the other devices should be slaves. Keywords: master, slave, contention, busy, CY7C130, CY7C131, CY7C132, CY7C133, CY7C136, CY7C140, CY7C141, CY7C142, CY7C143, CY7C146