Motorola M68CPU32BUG User Manual download pdf (Page 30)

OPERATING INSTRUCTIONS

M68332BCC/D 3-2 MOTOROLA

REV 1

3.2.1 Chip Select Usage

The MC68332 MCU has chip select signals that enable peripheral devices. The BCC requires

some of these chip selects for BCC operation making them unavailable to the user. Do not

remove the chip selects used by the BCC, or CPU32Bug will not operate. In addition to the chip

selects employed on the BCC, other chip selects are used elsewhere in the M68332EVK (refer to

Tables 3-1 through 3-3).

Depending on the user’s environment, any or all of the chip selects may be re-configured for an

alternate function (i.e., as I/O or address lines). Chip select pins used by the BCC and EVK

cannot be used in their alternate capacities.

Although a chip select (CS8 on Rev. A and CS4 on Rev. B and Rev. C BCCs) is dedicated for

the ABORT switch, the pin is not used. Instead the chip select decodes the interrupt acknowledge

(IACK) cycle in response to a level 7 interrupt generated by the ABORT switch. Refer the

System Integration Module User’s Manual (SIM32UM/AD) for more information.

When the BCC is not mounted on the M68300PFB Platform Board (PFB), these chip selects are

available to the user. Also if the PFB RAM/EPROM socket pairs (U1/U3, U2/U4) and

coprocessor socket U5 are not populated, the chip selects are available to the user.

Table 3-1. BCC Rev. A Chip Selection Summary

Signal Board/Chip Description Memory Type

CSBOOT BCC U2 CPU32Bug EPROM

CS0 BCC U1 read/write enable for MSB=UPPER=EVEN RAM

CS1 BCC U3 read/write enable for LSB=LOWER=ODD RAM

CS2 PFB U1/U3 read enable for MSB/LSB=BOTH RAM

CS3 PFB U1 write enable for LSB=LOWER=ODD RAM

CS4 PFB U4 read enable for MSB=UPPER=EVEN RAM/EPROM

CS5 PFB U2 read enable for LSB=LOWER=ODD RAM/EPROM

CS6 PFB U5 chip enable for MC68881/882

CS7 <unused>

CS8 PFB ABORT push-button autovector

CS9 <unused>

CS10 PFB U3 write enable for MSB=UPPER=EVEN

cut/jump U3-27 from CS4 to CS10 required.

RAM

1 2 ... 25 26 27 28 29 30 31 32 33 34 35 ... 67 68

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Motorola M68CPU32BUG User Manual Page 30