M32C80 Datasheet, PDF (58/352 Pages) Renesas Technology Corp – 16/32-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M32C/80 SERIES

M32C/80 Group
7. Bus
7. Bus
In memory expansion mode or microprocessor mode, some pins function as bus control pins to control the
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address bus and data bus. A0 to A22, A23, D0 to D15, CS0 to CS3, WRL/WR, WRH/BHE, RD, BCLK/ALE,
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HLDA/ALE, HOLD, ALE, RDY are used as bus control pins.
7.1 Bus Settings
The BYTE pin, the DS register, the PM05 and PM04 bits in the PM0 register, and the PM11 and PM10 bits
in the PM1 register determine bus settings.
Table 7.1 lists how to change bus settings. Figure 7.1 shows the DS register.
Table 7.1 Bus Settings
Bus Setting
Selecting External Address Bus Width
Setting Bus Width after Reset
Selecting Between Separate Bus or Multiplexed Bus
Number of Chip-select
Changed By
DS register
BYTE pin (external space 3 only)
PM05 and PM04 bits in PM0 register
PM11 and PM10 bits in PM1 register
External Data Bus Width Control Register
b7 b6 b5 b4 b3 b2 b1 b0
Symbol
DS
Address
000B16
After Reset
XXXX 10002 (BYTE pin = "L")
XXXX 00002 (BYTE pin = "H")
Bit
Symbol
Bit Name
Function
RW
DS0
External Space 0 Data
Bus Width Select Bit
0: 8 bits wide
1: 16 bits wide
RW
DS1
External Space 1 Data
Bus Width Select Bit
0: 8 bits wide
1: 16 bits wide
RW
DS2
External Space 2 Data
Bus Width Select Bit
0: 8 bits wide
1: 16 bits wide
RW
DS3
External Space 3 Data
Bus Width Select Bit
0: 8 bits wide
1: 16 bits wide
RW
Nothing is assigned. When write, set to "0".
(b7 - b4) ^{When read, its content is indeterminate.}
Figure 7.1 DS Register
Rev. 1.00 Nov. 01, 2005 Page 39 of 330
REJ09B0271-0100