7.5.3 Read RSWP
The Read RSWP command allows the ability to check a quadrant’s write protection status. To
find out if the software write protection has been set to a specific quadrant, the same
procedure that was used to set the quadrant’s write protection can be utilized except that
the R/W select bit is set to ‘1’, and the A0 pin is
not required to have VHV (see Table 7-5).
The Read RSWP sequence requires sending a device address byte of
‘0110MMM1’ (where the ‘M’ represents the memory quadrant identifier for
the quadrant to be read) with the R/W bit set to ‘1’
(see Figure 7-6).
If the RSWP has not been set, then the AT34C04 responds to the device address byte with an ACK. If the RSWP has been set, the AT34C04 responds with a NACK. In either case, both word address and data word bytes will not be acknowledged. The operation is completed by the master creating a Stop Condition. A summary of the response is shown in Table 7-4.
| Quadrant Status | Instruction Sent | Instruction Response | Word Address Sent | Word Address Response | Data Word Sent | Data Word Response |
|---|---|---|---|---|---|---|
| Write Protected | Read RSWP | NACK | Don’t Care | NACK | Don’t Care | NACK |
| Not Protected | Read RSWP | ACK | Don’t Care | NACK | Don’t Care | NACK |
| Function | Pin | Device Address Byte | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Device Type Identifier | Memory Quadrant Identifier | R/W Select | |||||||||
| A2 | A1 | A0 | B7 | B6 | B5 | B4 | B3 | B2 | B1 | B0 | |
| Read RSWP, Quadrant 0 | x | x |
or VHV | 0 | 1 | 1 | 0 | 0 | 0 | 1 | 1 |
| Read RSWP, Quadrant 1 | x | x | 1 | 0 | 0 | 1 | |||||
| Read RSWP, Quadrant 2 | x | x | 1 | 0 | 1 | 1 | |||||
| Read RSWP, Quadrant 3 | x | x | 0 | 0 | 0 | 1 | |||||
Xis ‘don’t care’, but it is recommend to be hard-wired to VCC or GND.
Mis the memory quadrant identifier.Xis ‘don’t care’.