ACE34AC04

4K I

VER 1.1

9

Reading the state of the SPA can be accomplished via the Read Page Address (RPA) command. The

Master can issue the RPA command to determine if the ACE34AC04’s internal address counter is located

in the first 2-Kbit section or the second 2-Kbit memory section based upon the device’s ACK or NACK

response to the RPA command. The RPA command sequence requires the Master to transmit a Start bit

followed by a control byte of‘01101101’ (6Dh). If the device’s current address counter (page address) is

located in the first half of the memory, the ACE34AC04 responds with an ACK to the RPA command.

Alternatively, a NACK response to the RPA command indicates the page address is located in the second

half of the memory .Following the control byte and the device’s ACK or NACK response, the ACE34AC04

should transmit two data bytes of don’t care values. The Master should NACK on these two data bytes

followed by the Master sending a Stop condition to end the operation. After power-up, the SPA is set to

zero indicating internal address counter is located in the first half of the memory.

Performing a software reset will also set the SPA to zero. The ACE34AC04 incorporates a Reversible

Software Write Protect (RSWP) feature that allows the ability to selectively write protect data stored in any

or all of the four 128-byte quadrants.

Figure 6: Read Page Address (RPA)

Write Operations

The ACE34AC04 supports single Byte Write and Page Write operations up to the maximum page size of

16 bytes in one operation. The only difference between a Byte Write and a Page Write operation is the

amount of data bytes sent to the device. Regardless of whether a Byte Write or Page Write operation is

performed, the internally self-timed write cycle will take the same amount of time to write the data to the

addressed memory location(s). All Byte Write and Page Write operations should be preceded by the SPA

and or RPA commands to ensure the internal address counter is located in the desired half of the memory.

If a Byte Write or Page Write operation is attempted to a protected quadrant, the ACE34AC04 will respond

(ACK or NACK) to the write operation according to Table 4.

Table 4: Acknowledge Status When Writing Data or Defining Write Protection

Quadrant Status

Instruction

ACK

Word Address

ACK

Data Word

ACK

Write

Cycle

Write Protected

with Set RSWP

Set RSWP

NACK

Don’t Care

NACK

Don’t Care

NACK

No

Clear RSWP

ACK

Don’t Care

ACK

Don’t Care

ACK

Yes

Byte Write or

Page Write

to Protected

Quadrant

ACK

Word Address

ACK

Data

ACK

No

Not Protected

Set RSWP or

Clear RSWP

ACK

Don’t Care

ACK

Don’t Care

ACK

Yes

Byte Write or

Page Write

ACK

Word Address

ACK

Data

ACK

Yes