DM163006 datasheet(71/320 Pages) MICROCHIP

71 / 320 page

 2001 Microchip Technology Inc.

Advance Information

DS39541A-page 71

PIC18C601/801

5.4.1

CHIP SELECT 1 (CS1)

CS1 is enabled by writing a value other than 00h into

either the CSEL2 register, or the CSELIO register. If

both of the chip select registers are programmed to

00h, the CS1 signal is not enabled and the RF5 pin is

configured as I/O.

CS1 is low for all addresses in which CS2 and CSELIO

are high. Therefore, if CSEL2 = 20h and CSELIO = 80h,

then the CS1 signal will be low for the address that falls

between 000000h and (2000h x 20h) - 1 = 03FFFFh.

CS1 will always be low for the lower 8K of program

memory. Figure 5-9 shows an example address map for

CS1.

5.4.2

CHIP SELECT 2 (CS2)

CS2 is enabled for program memory accesses, starting

at the address derived by the 8-bit value contained in

CSEL2. For example, if the value contained in the

CSEL2 register is 80h, then the CS2 signal will be

asserted low whenever the address is greater than or

equal to 2000h x 80h = 100000h.

A 00h value in the CSEL2 register will disable the CS2

signal and will configure the RF4 pin as I/O. Figure 5-9

shows an example address map for CS2.

5.4.3

CHIP SELECT I/O (CSIO)

CSIO is enabled for a fixed 8K address range starting

at the address defined by the 8-bit value contained in

CSELIO. If, for instance, the value contained in the

CSELIO register is 80h, then the CSIO signal will be

low for the address range between 100000h and

101FFFh.

If the 8K address block overlaps the address range

specified in the CSEL2 register, the CSIO signal will be

low, and the CS2 signal will be high, for that region.

A 00h value in the CSELIO register will disable the

CSIO signal and will configure the RF3 pin as I/O.

Figure 5-9 shows an example address map for CSIO.

FIGURE 5-9:

EXAMPLE CONFIGURATION ADDRESS MAP FOR CS1, CS2, AND CSIO

PROGRAM MEMORY

CSEL2 = FFh (DEFAULT)

CSELIO = FFh (DEFAULT)

= CS1 ACTIVE

= CS2 ACTIVE

= CSIO ACTIVE

000000h

1FFFFFh

PROGRAM MEMORY

CSEL2 = 80h

CSELIO = 00h

000000h

1FFFFFh

PROGRAM MEMORY

CSEL2 = 20h

CSELIO = 80h

000000h

1FFFFFh

100000h

0FFFFFh

100000h

101FFFh

102000h

0FFFFFh

03FFFFh

040000h

= NO CHIP SELECT ACTIVE

INTERNAL EXECUTION IF

PGRM = 1

1FFDFFh

1FFE00h

1FFDFFh

1FFE00h

1FFDFFh

1FFE00h

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