Motorola MVME172 manual Memory Space Data Width

4

IP2 Chip

WIDTH1	WIDTH0	Memory Space Data Width
0	0	32 bits
0	1	8 bits
1	0	16 bits
1	1	Reserved

Note When programming b_WIDTH1-b_WIDTH0 for either 8- bits or 16-bits, a_WIDTH1-a_WIDTH0 must be programmed for one of 8-bits or 16-bits. This applies whether or not a_MEN is set. For example, if offset $19 is set to the value $09, then offset $18 can be set to $04, $05, $08, or $09, but not to $00, or $01. The same relationship also pertains to IP_c and IP_d, i.e., when programming d_WIDTH1-d_WIDTH0 for either 8-bits or 16-bits, c_WIDTH1-c_WIDTH0 must be programmed for one of 8- bits or 16-bits. This applies whether or not c_MEN is set.

RT1, RT0 The recovery timers determine the time that must expire from the acknowledgment of an IndustryPack I/O, ID, or Interrupt Acknowledge cycle until the IP2 chip asserts a new I/O, ID, or Int SEL* to the same IndustryPack. This may help with some devices on IndustryPacks that require dead time between cycles. Each recovery timer’s counter starts incrementing at the assertion of its IPACK* signal and continues to increment until it matches the value encoded from its two recovery timer control bits. When it reaches that value, the recovery time has expired and a new cycle can be generated to the IndustryPack. The recovery timer counters are cleared at reset. The recovery times encoded by the recovery timer control bits are shown in the following table. When a double size IndustryPack is used at ab and the I/O space for ab is accessed in the double size address range, the RT bits for a and b should be programmed identically. The same pertains to the RT bits for c and d.

There are some restrictions for using recovery timers with double size IndustryPacks. When using a double size IndustryPack, programmed recovery times for back-to-

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