M32C8A Datasheet, PDF (67/372 Pages) Renesas Technology Corp – RENESAS MCU M16C FAMILY / M32C/80 Series

M32C/8A Group
8. Bus
8.1.1 Selecting External Address Bus
The number of external address bus pins, the number of chip-select pins, and chip-select-assigned address space
(CS area) vary in each external space mode. Bits PM11 and PM10 in the PM1 register select external space
mode.
8.1.2 Selecting External Data Bus
The DS register selects either external 8-bit data bus or 16-bit data bus per each external space. The data bus in
the external space 3, after reset, becomes 16 bits wide when a low-level (“L”) signal is applied to the BYTE pin
and 8 bits wide when a high-level (“H”) signal is applied. Keep the BYTE pin level while the MCU is
operating. Internal bus is always 16 bits wide.
8.1.3 Selecting Separate/Multiplexed Bus
Bits PM05 and PM04 in the PM0 register select either the separate bus or multiplexed bus. The MCU starts up
with the separate bus after reset.
8.1.3.1 Separate Bus
With the separate bus format, the MCU performs data input/output and address output using individual buses.
The DS register selects 8-bit or 16-bit external data bus for each external space. If all DSi bits in the DS register
(i = 0 to 3) are set to 0 (8-bit data bus), port P0 functions as the data bus and port P1 as the programmable I/O
port.
If any of the DSi bits is set to 1 (16-bit data bus), ports P0 and P1 function as the data bus. Port P1 output is
undefined when the MCU accesses the space where its DSi bit is set to 0.
8.1.3.2 Multiplexed Bus
With the multiplexed bus format, the MCU performs data input/output and address output using the same bus
by time-sharing. D0 to D7 are time-multiplexed with A0 to A7 in the space accessed by the 8-bit data bus. D0
to D15 are time-multiplexed with A0 to A15 in the space accessed by the 16-bit data bus.
Table 8.2 lists multiplexed bus settings and chip-select areas. Table 8.3 lists a processor mode and pin function.
Table 8.2 Multiplexed Bus Settings and Chip-Select Areas
PM05 and PM04
bits setting⁽¹⁾
00b
(multiplexed bus not used)
01b
(access the CS2 area
using multiplexed bus)
10b
(access the CS1 area
using multiplexed bus)
00b
(external space
mode 0
Do not set to
these values
PM11 and PM10 Bits Setting
01b
(external space
mode 1)
10b
(external space
mode 2)
Separate bus
CS2
Do not set to
this value
CS1
CS1
NOTE:
1. In microprocessor mode, do not set bits PM05 and PM04 in the PM0 register to 11b.
11b
(external space
mode 3)
CS2
CS1
Rev.1.00 Jul 15, 2007 Page 50 of 352
REJ09B0385-0100