32186 datasheet(826/1032 Pages) RENESAS

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EXTERNAL BUS INTERFACE

17-16

32185/32186 Group Hardware Manual

Rev.1.10 REJ09B0235-0110 May 15, 07

17.2 External Bus Interface Related Registers

17.2.3 CLKOUT Select Register

CLKOUT Select Register (CLKOUTSEL)

<Address: H'0080 01A0>

123456

CLKOSEL

CLKOSELP

Bit Name

Function

0–5

No function assigned. Fix to"0."

CLKOSELP

CLKOSEL write control bit

CLKOSEL

0: BCLK divided by 2

CLKOUT select bit

1: BCLK

Notes: • When CLKOUT changes from divided-by-2 BCLK to straight BCLK or vice versa, there will be some hazards riding on

CLKOUT.

• When BCLK is selected as a CLKOUT terminal output, regardless of CS0 to CS3 are used or not, it is prohibition that

selecting 0 wait in WAIT (the number selection of internal wait) bit of a CSx area wait control register.

(1) CLKOSELP (CLKOSEL Write Control) bit (Bit 6)

This bit controls write to the CLKOUT select bit.

(2) CLKOSEL (CLKOUT Select) bit (Bit 7)

This bit selects straight BCLK or divided-by-2 BCLK as outputting of CLKOUT (external bus synchronous

clock) pin. If the CPU clock is 80 MHz, BCLK is 20 MHz. If CLKOSEL is cleared to "0," CLKOUT or the

external bus reference clock is 10 MHz; if CLKOSEL is set to "1," CLKOUT is 20 MHz. The number of wait

states set by the CSn area wait control register, as well as CSn wait, strobe wait, recovery cycles and idle

cycles after read all are synchronized to CLKOUT.

However when "1" is selected in CLKOSEL bit (BCLK is selected as a CLKOUT terminal output), regardless

of CS0 to CS3 are used or not, it is prohibition that selecting 0 wait in WAIT (the number selection of internal

wait) bit of a CSn area wait control register.

The following describes how to set the CLKOSEL bit.

1. The program in the internal ROM or the internal RAM should be used to set the bits.

2. Write "1" to the CLKOSEL write control bit (CLKOSELP). (See Figure 17.2.2.)

3. Subsequent to 2 above, write "0" to the CLKOSEL write control bit (CLKOSELP) and then "0"

or "1" whichever desired to the CLKOUT select bit (CLKOSEL).

4. After writing to the above bits, access any SFR area for read twice.

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