M69KB096AA datasheet(13/48 Pages) STMICROELECTRONICS

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M69KB096AA

CONFIGURATION REGISTERS

Two write-only user-accessible configuration reg-

isters have been included to define device opera-

tion. These registers are automatically loaded with

default settings during power-up, and can be up-

dated any time the device is operating in a standby

state.

The configuration registers (BCR and RCR) can

be programmed and read using two methods:

■

The CR Controlled Method (or Hardware

Method)

■

The Software Method.

Programming and Reading the Configuration

Registers using the CR Controlled Method

The BCR and the RCR can be programmed and

read using either a Synchronous or an Asynchro-

nous Write and Read operation with the Configu-

ration Register Enable input, CR, at VIH. Address

bit A19 selects the register to be programmed or

read (see Table 4., Register Selection). The val-

ues placed on address lines A0 to A21 are latched

into the register on the rising edge of L, E, or W,

whichever occurs first. LB and UB are “don’t care”.

When CR is at VIL, a Read or Write operation will

access the memory array.

See Figures 27 and 33, Configuration Register

Write in Asynchronous and Synchronous Modes.

Table 4. Register Selection

Programming and Reading the Configuration

Registers by the Software Method

Each register can be read by issuing a Read Con-

figuration Register sequence (see Figure 9., Read

Configuration Register (Software Method), and

programmed by issuing a Set Configuration Reg-

ister sequence (see Figure 8., Set Configuration

must be issued in asynchronous mode.

The timings will be identical to those described in

Table 15., Asynchronous Read AC Characteris-

tics. The Chip Enable input, CR, is ‘don’t care’.

Read Configuration Register and Set Configura-

tion Register sequences both require 4 cycles:

■

2 bus read and one bus write cycles to a

unique address location, 3FFFFFh, indicate

that the next operation will read or write to a

configuration register. The data written during

the third cycle must be ‘0000h’ to access the

RCR and ‘0001h’ to access the BCR during

the next cycle.

■

The fourth cycle reads from or writes to the

configuration register.

Read or Write Operation

A19

RCR

Read/Write

BCR

Read/Write

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