DS1963L

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MEMORY FUNCTION COMMANDS

The “Memory Function Flow Chart” (Figure 7) describes the protocols necessary for accessing the

memory. An example follows the flowchart. The communication between master and DS1963L takes

place either at regular speed (default, OD = 0) or at Overdrive speed (OD = 1). If not explicitly set into

the Overdrive mode the DS1963L assumes regular speed.

Write Scratchpad Command [0FH]

After issuing the write scratchpad command, the master must first provide the 2-byte target address,

followed by the data to be written to the scratchpad. The data will be written to the scratchpad starting at

the byte offset (T4:T0). The ending offset (E4: E0) will be the byte offset at which the master stops

writing data. Only full data bytes are accepted. If the last data byte is incomplete its content will be

ignored and the partial byte flag PF will be set.

When executing the Write Scratchpad command the CRC generator inside the DS1963L (see Figure 12)

calculates a CRC over the entire data stream, starting at the command code and ending at the last data

byte sent by the master. This CRC is generated using the CRC16 polynomial by first clearing the CRC

generator and then shifting in the command code (0FH) of the Write Scratchpad command, the Target

Addresses TA1 and TA2 as supplied by the master and all the data bytes. The master may end the Write

Scratchpad command at any time. However, if the ending offset is 11111b, the master may send 16 read

time slots and will receive the CRC generated by the DS1963L.

The memory address range of the DS1963L is 0000H to 01FFH. If the bus master sends a target address

higher than this, the internal circuitry of the chip will set the seven most significant address bits to 0 as

they are shifted into the internal address register. The Read Scratchpad command will reveal the target

address as it will be used by the DS1963L. The master will identify such address modifications by

comparing the target address read back to the target address transmitted. If the master does not read the

scratchpad, a subsequent copy scratchpad command will not work since the most significant bits of the

target address the master sends will not match the value the DS1963L expects.

Read Scratchpad Command [AAH]

This command is used to verify scratchpad data and target address. After issuing the read scratchpad

command, the master begins reading. The first 2 bytes will be the target address. The next byte will be the

ending offset/data status byte (E/S) followed by the scratchpad data beginning at the byte offset (T4: T0).

The master may read data until the end of the scratchpad after which the data read will be all logic 1’s.

Copy Scratchpad [5AH]

This command is used to copy data from the scratchpad to memory. After issuing the copy scratchpad

command, the master must provide a 3-byte authorization pattern which can be obtained by reading the

scratchpad for verification. This pattern must exactly match the data contained in the three address

registers (TA1, TA2, E/S, in that order). If the pattern matches, the AA (Authorization Accepted) flag

will be set and the copy will begin. A pattern of alternating 1s and 0s will be transmitted after the data has

been copied until a reset pulse is issued by the master. Any attempt to reset the part will be ignored while

the copy is in progress. Copy typically takes 30

µs.

The data to be copied is determined by the three address registers. The scratchpad data from the

beginning offset through the ending offset, will be copied to memory, starting at the target address.

Anywhere from 1 to 32 bytes may be copied to memory with this command. The AA flag will be cleared

only by executing a write scratchpad command.