Intel 87C196CB, 8XC196NT Interfacing With External Memory, Address Pins, Bus Timing Modes

CHAPTER 9 INTERFACING WITH EXTERNAL MEMORY

The 87C196CB’s external memory interface is similar to that of the 8XC196NT. However, the 87C196CB supports only two of the bus timing modes, modes 3 and 0. In addition, the 100-pin 87C196CB has four additional address pins (A23:20).

9.1ADDRESS PINS

The 100-pin 87C196CB has 24 available address pins, A23:16 and AD15:0. The A23:20 timings are identical to those of A19:16. During the CCB fetch, the 100-pin 87C196CB strongly drives 0FFH on A23:16. The 84-pin 87C196CB strongly drives 0FH on A19:16, as does the 8XC196NT.

9.2BUS TIMING MODES

The 87C196CB implements only modes 3 and 0. Table 9-1 and Figure 9-1 compare the timings of these two modes. Figure 9-2 illustrates the CCB1 register, which selects the mode.

Table 9-1. Modes 0 and 3 Timing Comparisons

Mode			Timing Specifications †
	TCLLH	TAVLL	TAVDV	TRLRH	TRHDZ	TRLDV
Mode 3	0	1t	3t	1t	1t	1t
Mode 0	0	1t	5t	3t	1t	3t

†These are ideal timing values for purposes of comparison only. They do not include internal device delays. Consult the datasheet for current device specifications.

9-1