M16C6NK Datasheet, PDF (66/404 Pages) Renesas Technology Corp – 16-BIT SINGLE-CHIP MICROCOMPUTER M16C FAMILY / M16C/60 SERIES

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M16C/6N Group (M16C/6NK, M16C/6NM)
7. Bus
7.2.4 Read and Write Signals
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When the data bus is 16-bit width, the read and write signals can be chosen to be a combination of RD,
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WR and BHE or a combination of RD, WRL and WRH by using the PM02 bit in the PM0 register. When
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the data bus is 8-bit width, use a combination of RD, WR and BHE.
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Table 7.3 shows the operation of RD, WRL, and WRH signals. Table 7.4 shows the operation of RD, WR,
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and BHE signals.
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Table 7.3 Operation of RD, WRL and WRH Signals
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Data Bus Width
RD
WRL
WRH
16 Bits
L
H
H
(BYTE pin
H
L
H
input = L)
H
H
L
H
L
L
Status of External Data Bus
Read data
Write 1 byte of data to an even address
Write 1 byte of data to an odd address
Write data to both even and odd addresses
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Table 7.4 Operation of RD, WR and BHE Signals
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Data Bus Width RD
WR
BHE
A0
16 Bits
H
L
L
H
(BYTE pin
L
H
L
H
input = L) H
L
H
L
L
H
H
L
H
L
L
L
L
H
L
L
8 Bits
H
L Not used H to L
(BYTE pin input = H)
L
H Not used H to L
Status of External Data Bus
Write 1 byte of data to an odd address
Read 1 byte of data from an odd address
Write 1 byte of data to an even address
Read 1 byte of data from an even address
Write data to both even and odd addresses
Read data from both even and odd addresses
Write 1 byte of data
Read 1 byte of data
7.2.5 ALE Signal
The ALE signal latches the address when accessing the multiplexed bus space. Latch the address when
the ALE signal falls. Figure 7.3 shows the ALE signal, address bus and data bus.
When BYTE pin input = H
ALE
A0/D0 to A7/D7
Address
Data
When BYTE pin input = L
ALE
A0
Address
A8 to A19
Address ⁽¹⁾
A1/D0 to A8/D7
Address
Data
A9 to A19
NOTE:
1. If the entire CS space is assigned a multiplexed bus, these pins function as I/O ports.
Address
Figure 7.3 ALE Signal, Address Bus, Data Bus
Rev.2.00 Nov 28, 2005 page 48 of 378
REJ09B0124-0200