Intel 80C196NU manual Write Signals for Standard and Write Strobe Modes, Ale Wr# Wrl#, Bhe# Wrh#

8XC196NP, 80C196NU USER’S MANUAL

Standard Mode	Write Strobe Mode
ALE	ALE
WR#	WRL#
Active for low- or high-byte write.	Active for low-byte write.
BHE#	WRH#
Active for high-byte write.	Active for high-byte write.

A2472-02

Figure 13-17. Write-control Signal Waveforms

Table 13-14 compares the values of the write-control signals for write operations in the standard mode and the write strobe mode. The table lists values of WR# and BHE# and values of WRL# and WRH# for 8-bit and 16-bit writes on an 8-bit and 16-bit bus.

Table 13-14. Write Signals for Standard and Write Strobe Modes

Bus	Word/Byte		Standard			Write Strobe
		A0	(CCR0.2 = 1)			(CCR0.2 = 0)
Width	Written
			WR#		BHE#	WRL#	WRH#
	Low Byte	0	0		1	0	0
8	High Byte	1	0		0	0	0
	Word	0	0		0	0	0
		1		Illegal		Illegal
	Low Byte	0	0	1		0	1
16	High Byte	1	0	0		1	0
	Word	0	0	0		0	0
		1		Illegal		Illegal

To select the standard write-control mode, set CCR0.2. In standard mode, the WR#/WRL# pin operates as WR#, and the BHE#/WRH# pin operates as BHE#. WR# is asserted for every external memory write. BHE# is asserted for word accesses (read and write) and for byte accesses to odd addresses. BHE# can be used to select the bank of memory that stores the high (odd) byte. Figure 13-10 on page 13-22 illustrates use of the standard mode in a 16-bit system. In this example, WR# writes words to the 16-bit flash memory. To write individual bytes, you can use the decoding logic in Figure 13-18 or use the write strobe mode.

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