M32CSLASH86 datasheet(83/505 Pages) RENESAS

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Page 60

8. Bus

)

(

8.2.4 Bus Timing

Bus cycle for the internal ROM and internal RAM is basically one BCLK cycle. When the PM12 bit in the

PM1 register is set to "1" (wait state), the bus cycles are two BCLK cycles.

Bus cycles for the SFR are basically two BCLK cycles. When the PM13 bit in the PM1 register is set to "1"

(2 wait states), the bus cycles are three BCLK cycles.

Basic bus cycle for an external space is 2ø (1ø+1ø) to read and to write. Bus cycle is selected by the

EWCRi register (i=0 to 3) from 12 types of separate bus settings and 7 types of multiplexed bus settings.

If the EWCRi04 to EWCRi00 bits are set to "000112" (1ø+3ø), bus cycles are four BCLK cycles.

Figure 8.3 shows the EWCRi register. Figures 8.4 to 8.8 show bus timing in an external space.

Figure 8.3 EWCR0 to EWCR3 Registers

Symbol

Address

After Reset

EWCR0 to EWCR3

004816, 004916, 004A16, 004B16

X0X0 00112

External Space Wait Control Register i (i=0 to 3)(3)

EWCRi00

EWCRi01

EWCRi03

EWCRi04

(b5)

(b7)

EWCRi06

EWCRi02

0 0 0 0 1: 1

φ + 1φ

0 0 0 1 0: 1

φ + 2φ

0 0 0 1 1: 1

φ + 3φ

0 0 1 0 0: 1

φ + 4φ

0 0 1 0 1: 1

φ + 5φ

0 0 1 1 0: 1

φ + 6φ

0 1 0 1 0: 2

φ + 2φ

0 1 0 1 1: 2

φ + 3φ

0 1 1 0 0: 2

φ + 4φ

0 1 1 0 1: 2

φ + 5φ

1 0 0 1 1: 3

φ + 3φ

1 0 1 0 0: 3

φ + 4φ

1 0 1 0 1: 3

φ + 5φ

1 0 1 1 0: 3

φ + 6φ

Do not set values other than the above

Bit Name

Function

Bit

Symbol

Bus Cycle Select Bit

Nothing is assigned.

When read, its content is indeterminate.

Nothing is assigned.

When read, its content is indeterminate.

Recovery Cycle Addition

Select Bit

0 : Adds no recovery cycle when

accessing external space i

1 : Adds a recovery cycle when

accessing external space i

b4 b3 b2 b1 b0

(1)

(2)

NOTES:

1. The number of bus cycles from "when bus access begins" to "when RD or WR signal becomes "L".

2. The number of bus cycles from "when RD or WR signal becomes "L" to "when it becomes "H".

3. The EWCR0 to EWCR3 registers in M32C/86T cannot be used.

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