Cypress CY7C602xx WriteBlock Function, 5. WriteBlock Parameters, EraseBlock Function, Mode, Name

CY7C601xx, CY7C602xx

11.5.3 WriteBlock Function

The WriteBlock function is used to store data in Flash. Data is moved 64 bytes at a time from SRAM to Flash using this function. The WriteBlock function first checks the protection bits and deter- mines if the desired BLOCKID is writable. If write protection is turned on, the WriteBlock function exits setting the accumulator and KEY2 back to 00h. KEY1 has a value of 01h, indicating a write failure. The configuration of the WriteBlock function is straightforward. The BLOCKID of the Flash block, where the data is stored, is determined and stored at SRAM address FAh.

The SRAM address of the first of the 64 bytes to be stored in Flash is indicated using the POINTER variable in the parameter block (SRAM address FBh). Finally, the CLOCK and DELAY value are set correctly. The CLOCK value determines the length of the write pulse used to store the data in Flash. The CLOCK and DELAY values are dependent on the CPU speed and must be set correctly. Refer to the Clocking section for additional infor- mation.

Table 11-5. WriteBlock Parameters

Name	Address	Description
KEY1	0,F8h	3Ah
KEY2	0,F9h	Stack Pointer value, when SSC is
		executing
BLOCK ID	0,FAh	8 KB Flash block number (00h–7Fh)
		4 KB Flash block number (00h–3Fh)
		3 KB Flash block number (00h–2Fh)
POINTER	0,FBh	First 64 addresses in SRAM where
		the data is stored in Flash is located
		before calling WriteBlock
CLOCK	0,FCh	Clock Divider used to set the write
		pulse width
DELAY	0,FEh	For a CPU speed of 12 MHz set to 56h

11.5.4 EraseBlock Function

The EraseBlock function is used to erase a block of 64 contiguous bytes in Flash. The EraseBlock function first checks the protection bits and determines if the desired BLOCKID is writable. If write protection is turned on, the EraseBlock function exits setting the accumulator and KEY2 back to 00h. KEY1 has a value of 01h, indicating a write failure. The EraseBlock function is only useful as the first step in programming. Erasing a block does not make data in a block fully unreadable. If the objective is to obliterate data in a block, the best method is to perform an EraseBlock followed by a WriteBlock of all zeros.

To set up the parameter block for EraseBlock, correct key values must be stored in KEY1 and KEY2. The block number to be erased is stored in the BLOCKID variable and the CLOCK and DELAY values are set based on the current CPU speed.

Table 11-6. EraseBlock Parameters

Name	Address	Description
KEY1	0,F8h	3Ah
KEY2	0,F9h	Stack Pointer value, when SSC is
		executed
BLOCKID	0,FAh	Flash block number (00h–7Fh)
CLOCK	0,FCh	Clock Divider used to set the erase
		pulse width
DELAY	0,FEh	For a CPU speed of 12 MHz set to
		56h

11.5.5 ProtectBlock Function

The enCoRe II LV devices offer Flash protection on a block-by-block basis. Table 11-7lists the protection modes available. In the table, ER and EW indicate the ability to perform external reads and writes; IW is used for internal writes. Internal reading is always permitted using the ROMX instruction. The ability to read using the SROM ReadBlock function is indicated by SR. The protection level is stored in two bits according to Table 11-7. These bits are bit packed into 64 bytes of the protection block. Therefore, each protection block byte stores the protection level for four Flash blocks. The bits are packed into a byte, with the lowest numbered block’s protection level stored in the lowest numbered bits in Table 11-7.

The first address of the protection block contains the protection level for blocks 0 through 3; the second address is for blocks 4 through 7. The 64th byte stores the protection level for blocks 252 through 255.

Table 11-7. Protection Modes

Mode	Settings				Description	Marketing
00b	SR ER EW IW				Unprotected	Unprotected
01b	SR	ER	EW IW		Read protect	Factory upgrade
10b	SR	ER	EW	IW	Disable external	Field upgrade
					write
11b	SR	ER	EW	IW	Disable internal	Full protection
					write

7	6	5	4	3	2	1	0
Block	n+3	Block	n+2	Block	n+1	Block n

Only an EraseAll decreases the protection level by placing zeros in all locations of the protection block. To set the level of protection, the ProtectBlock function is used. This function takes data from SRAM, starting at address 80h, and ORs it with the current values in the protection block. The result of the OR operation is then stored in the protection block. The EraseBlock function does not change the protection level for a block. Because the SRAM location for the protection data is fixed and there is only one protection block per Flash macro, the Protect- Block function expects very few variables in the parameter block to be set before calling the function. The parameter block values that are, besides the keys, are the CLOCK and DELAY values.

Document 38-16016 Rev. *E Page 17 of 68

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