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FM93C66A Datasheet(PDF) 5 Page - Fairchild Semiconductor |
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FM93C66A Datasheet(HTML) 5 Page - Fairchild Semiconductor |
5 / 13 page 5 www.fairchildsemi.com FM93C66A Rev. B.1 Pin Description Chip Select (CS) This is an active high input pin to FM93C66A EEPROM (the device) and is generated by a master that is controlling the device. A high level on this pin selects the device and a low level deselects the device. All serial communications with the device is enabled only when this pin is held high. However this pin cannot be permanently tied high, as a rising edge on this signal is required to reset the internal state-machine to accept a new cycle and a falling edge to initiate an internal programming after a write cycle. All activity on the SK, DI and DO pins are ignored while CS is held low. Serial Clock (SK) This is an input pin to the device and is generated by the master that is controlling the device. This is a clock signal that synchronizes the communication between a master and the device. All input informa- tion (DI) to the device is latched on the rising edge of this clock input, while output data (DO) from the device is driven from the rising edge of this clock input. This pin is gated by CS signal. Serial Input (DI) This is an input pin to the device and is generated by the master that is controlling the device. The master transfers Input informa- tion (Start bit, Opcode bits, Array addresses and Data) serially via this pin into the device. This Input information is latched on the rising edge of the SCK. This pin is gated by CS signal. Serial Output (DO) This is an output pin from the device and is used to transfer Output data via this pin to the controlling master. Output data is serially shifted out on this pin from the rising edge of the SCK. This pin is active only when the device is selected. Organization (ORG) This is an input pin to the device and is used to select the format of data (16-bit or 8-bit). If this pin is tied high, 16-bit format is selected, while if it is tied low, 8-bit format is selected. Depending on the format selected, FM93C66A requires 8-bit address field (for 16-bit data format) or 9-bit address field (for 8-bit data format). Refer Table 1 and Table 2 for more details. This pin is internally pulled-up to VCC. Hence leaving this pin unconnected would default to 16-bit data format. Microwire Interface A typical communication on the Microwire bus is made through the CS, SK, DI and DO signals. To facilitate various operations on the Memory array, a set of 7 instructions are implemented on FM93C66A. The format of each instruction is listed under Table 1 (for 16-bit format) and Table 2 (for 8-bit format). Instruction Each of the above 7 instructions is explained under individual instruction descriptions. Start bit This is a 1-bit field and is the first bit that is clocked into the device when a Microwire cycle starts. This bit has to be “1” for a valid cycle to begin. Any number of preceding “0” can be clocked into the device before clocking a “1”. Opcode This is a 2-bit field and should immediately follow the start bit. These two bits (along with 2 MSB of address field) select a particular instruction to be executed. Address Field Depending on the selected organization, this is a 8-bit or 9-bit field and should immediately follow the Opcode bits. In FM93C66A, all 8 bits (or 9 bits) are used for address decoding during READ, WRITE and ERASE instructions. During all other instructions, the MSB 2 bits are used to decode instruction (along with Opcode bits). Data Field Depending on the selected organization, this is a 16-bit or 8-bit field and should immediately follow the Address bits. Only the WRITE and WRALL instructions require this field. MSB bit (D15 or D7) is clocked first and LSB bit (D0) is clocked last (both during writes as well as reads). Table 1. Instruction set (16-bit organization) Instruction Start Bit Opcode Field Address Field Data Field READ 1 10 A7 A6 A5 A4 A3 A2 A1 A0 WEN 1 00 1 1 XXXXXX WRITE 1 01 A7 A6 A5 A4 A3 A2 A1 A0 D15-D0 WRALL 1 00 0 1 XXXXXX D15-D0 WDS 1 00 0 0 XXXXXX ERASE 1 11 A7 A6 A5 A4 A3 A2 A1 A0 ERAL 1 00 1 0 XXXXXX |
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Similar Description - FM93C66A |
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