7.5.3 Hardware Write Protection

The WP pin can be connected to V_CC, GND, or left floating. Connecting the WP pin to V_CC will write-protect the entire array whether or not the Software Write Protection has been enabled or invoked (see Table 7-3 and Table 7-4). The Software Write Protection register cannot be programmed when the WP pin is connected to V_CC. If the WP pin is connected to GND or left floating, the write protection mode is determined by the status of the Software Write-Protect register.

Table 7-2. Write Protection
Command	Pin			Preamble							R/W
Command	A2	A1	A0	Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0
Set PSWP	A2	A1	A0	`0`	`1`	`1`	`0`	A2	A1	A0	`0`
Set RSWP	`0`	`0`	V_HV	`0`	`1`	`1`	`0`	`0`	`0`	`1`	`0`
Clear RSWP	`0`	V_CC	V_HV	`0`	`1`	`1`	`0`	`0`	`1`	`1`	`0`

Table 7-3. WP Connected to GND or Floating
WP Connected to GND or Floating
Command	R/W Bit	Permanent Write‑Protect Register PSWP	Reversible Write‑Protect Register RSWP	Response from Device	Action from Device
1010	R	X	X	ACK	Read Array.
1010	W	Programmed	X	ACK	Can write to second half (80h - FFh) only.
1010	W	X	Programmed	ACK	Can write to second half (80h - FFh) only.
1010	W	Not Programmed	Not Programmed	ACK	Can write to full array.
Read PSWP	R	Programmed	X	NACK	STOP – Indicates Permanent Write‑Protect register is programmed.
Read PSWP	R	Not Programmed	X	ACK	Data read out is undefined. Indicates PSWP register is not programmed.
Set PSWP	W	Programmed	X	NACK	STOP – Indicates Permanent Write‑Protect register is programmed.
Set PSWP	W	Not Programmed	X	ACK	Program Permanent Write‑Protect register (irreversible).
Read RSWP	R	X	Programmed	NACK	STOP – Indicates Permanent Write‑Protect register is programmed.
Read RSWP	R	X	Not Programmed	ACK	Data read out is undefined. Indicates RSWP register is not programmed.
Set RSWP	W	X	Programmed	NACK	STOP – Indicates Reversible Write‑Protect register is programmed.
Set RSWP	W	X	Not Programmed	ACK	Program Reversible Write‑Protect register (reversible).
Clear RSWP	W	Programmed	X	NACK	STOP – Indicates Permanent Write‑Protect register is programmed.
Clear RSWP	W	Not Programmed	X	ACK	Clear (unprogram) Reversible Write‑Protect register (reversible).

Table 7-4. WP Connected to V_CC
WP Connected to V_CC
Command	R/W Bit	Permanent Write‑Protect Register PSWP	Reversible Write‑Protect Register RSWP	Response from Device	Action from Device
`1010`	R	X	X	ACK	Read array.
`1010`	W	X	X	ACK	Device is write protected.
Read PSWP	R	Programmed	X	NACK	STOP – Indicates Permanent Write‑Protect register is programmed.
Read PSWP	R	Not Programmed	X	ACK	Data read out is undefined. Indicates PSWP register is not programmed.
Set PSWP	W	Programmed	X	NACK	STOP – Indicates Permanent Write‑Protect register is programmed.
Set PSWP	W	Not Programmed	X	ACK	Cannot program write‑protect registers.
Read RSWP	R	X	Programmed	NACK	STOP – Indicates Reversible Write‑Protect register is programmed.
Read RSWP	R	X	Not Programmed	ACK	Data read out is undefined. Indicates RSWP register is not programmed.
Set RSWP	W	X	Programmed	NACK	STOP – Indicates Reversible Write‑Protect register is programmed.
Set RSWP	W	X	Not Programmed	ACK	Cannot program write‑protect registers.
Clear RSWP	W	Programmed	X	NACK	STOP – Indicates Permanent Write‑Protect register is programmed.
Clear RSWP	W	Not Programmed	X	ACK	Cannot write to Write‑Protect registers.