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X9418WP24-2.7 Datasheet(PDF) 4 Page - Xicor Inc. |
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X9418WP24-2.7 Datasheet(HTML) 4 Page - Xicor Inc. |
4 / 21 page X9418 Characteristics subject to change without notice. 4 of 21 REV 1.1.5 7/23/02 www.xicor.com Acknowledge Polling The disabling of the inputs, during the internal nonvolatile write operation, can be used to take advantage of the typical 5ms EEPROM write cycle time. Once the stop condition is issued to indicate the end of the nonvolatile write command the X9418 initiates the internal write cycle. ACK polling can be initiated immediately. This involves issuing the start condition followed by the device slave address. If the X9418 is still busy with the write operation no ACK will be returned. If the X9418 has completed the write operation an ACK will be returned, and the master can then proceed with the next operation. Flow 1. ACK Polling Sequence Instruction Structure The next byte sent to the X9418 contains the instruction and register pointer information. The four most significant bits are the instruction. The next four bits point to one of the two pots and when applicable they point to one of four associated registers. The format is shown below in Figure 2. Figure 2. Instruction Byte Format The four high order bits define the instruction. The next two bits (R1 and R0) select one of the four registers that is to be acted upon when a register oriented instruction is issued. The last bits (P0) select which one of the two potentiometers is to be affected by the instruction. Bit 1 is defined to be 0. Four of the nine instructions end with the transmission of the instruction byte. The basic sequence is illustrated in Figure 3. These two-byte instructions exchange data between the wiper counter register and one of the data registers. A transfer from a Data Register to a Wiper Counter Register is essentially a write to a static RAM. The response of the wiper to this action will be delayed tWRL. A transfer from the wiper counter register (current wiper position), to a Data Register is a write to nonvolatile memory and takes a minimum of tWR to complete. The transfer can occur between one of the two potentiometers and one of its associated registers; or it may occur globally, wherein the transfer occurs between both of the potentiometers and one of their associated registers. Four instructions require a three-byte sequence to complete. These instructions transfer data between the host and the X9418; either between the host and one of the Data Registers or directly between the host and the wiper counter register. These instructions are: Read Wiper Counter Register (read the current wiper position of the selected pot), write Wiper Counter Register (change current wiper position of the selected pot), read Data Register (read the contents of the selected nonvolatile register) and write Data Register (write a new value to the selected Data Register). The sequence of operations is shown in Figure 4. Nonvolatile Write Command Completed Enter ACK Polling Issue START Issue Slave Address ACK Returned? Further Operation? Issue Instruction Issue STOP NO YES YES Proceed Issue STOP NO Proceed I1 I2 I3 I0 R1 R0 0 P0 Wiper Counter Register Select Register Select Instructions |
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