M32C8A Datasheet, PDF (66/372 Pages) Renesas Technology Corp – RENESAS MCU M16C FAMILY / M32C/80 Series

M32C/8A Group
8. Bus
8. Bus
In microprocessor mode, the following pins become bus control pins: D0 to D15, A0 to A22, A23, CS0 to CS3, WRL/
WR, WRH/BHE, RD, CLKOUT/BCLK/ALE, HLDA/ALE, HOLD, ALE, RDY.
8.1 Bus Settings
Bus setting is determined by the BYTE pin, the DS register, the PM05 and PM04 bits in the PM0 register, and bits
PM11 and PM10 in the PM1 register.
Table 8.1 lists how to change bus settings. Figure 8.1 shows the DS register.
Table 8.1 Bus Settings
Bus Setting
Selecting external data bus width
Setting bus width after reset
Selecting separate bus or multiplexed bus
Number of chip-select pins
Pin & Registers Used for Setting
DS register
BYTE pin (for external space 3 only)
Bits PM05 and PM04 in the PM0 register
Bits PM11 and PM10 in the PM1 register
External Data Bus Width Control Register
b7 b6 b5 b4 b3 b2 b1 b0
Symbol
DS
Address
000Bh
After Reset
XXXX 1000b (BYTE pin = "L")
XXXX 0000b (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⁽¹⁾
0: 8 bits wide
1: 16 bits wide
RW
−
(b7-b4)
Unimplemented.
Write 0. Read as undefined value.
−
Figure 8.1 DS Register
Rev.1.00 Jul 15, 2007 Page 49 of 352
REJ09B0385-0100