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DSEL

Delay Select Bit

This bit selects the delay that it takes for the cycle counter and the interval timer (in auto mode) to see a

transition on the data line. When this bit is set to a logic 1, the delay time is 123

± 2ms. This delay allows

communication on the data line without starting or stopping the interval timer and without incrementing

the cycle counter. When this bit is set to a logic 0, the delay time is 3.5

± 0.5ms.

MEMORY FUNCTION COMMANDS

The Memory Function Flowchart (Figure 6) describes the protocols necessary for accessing the memory.

An example follows the flowchart. Three address registers are provided as shown in Figure 5. The first

two registers represent a 16-bit target address (TA1, TA2). The third register is the ending offset/data

status Byte (E/S).

The target address points to a unique Byte location in memory. The first 5 bits of the target address

(T4:T0) represent the Byte offset within a page. This Byte offset points to one of 32 possible Byte

locations within a given page. For instance, 00000b points to the first Byte of a page where as 11111b

would point to the last Byte of a page.

The third register (E/S) is a read only register. The first 5 bits (E4:E0) of this register are called the

ending offset. The ending offset is a Byte offset within a page (1 of 32 Bytes). Bit 5 (PF) is the partial

Byte flag. Bit 6 (OF) is the overflow flag. Bit 7 (AA) is the authorization accepted flag.

Figure 5. ADDRESS REGISTERS

76543210

TARGET ADDRESS (TA1)

T7

T6

T5

T4

T3

T2

T1

T0

TARGET ADDRESS (TA2)

T15

T14

T13

T12

T11

T10

T9

T8

ENDING ADDRESS WITH

DATA STATUS (E/S)

(READ ONLY)

AA

OF

PF

E4

E3

E2

E1

E0

Write Scratchpad Command [0Fh]

After issuing the write scratchpad command, the user must first provide the 2-Byte target address,

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

Byte offset (T4:T0). The ending offset (E4:E0) is the Byte offset at which the host stops writing data. The

maximum ending offset is 11111b (31d). If the host attempts to write data past this maximum offset, the

overflow flag (OF) is set and the remaining data is ignored. If the user writes an incomplete Byte and an

overflow has not occurred, the partial Byte flag (PF) is set.

Read Scratchpad Command [AAh]

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

command, the user can begin reading. The first two Bytes are the target address. The next Byte is the