II CORE BLOCK: BCU (Bus Control Unit)
Using Internal Memory on External Memory Area
The BCU allows using of an internal memory in the external memory areas.
The AxxIO bit in the access control register (0x48132) is used to select either internal access or external access. When "1" is written, the internal device will be accessed and when "0" is written, the external device is accessed (external access by default). The bit names and the corresponding areas are as follows:
A18IO (DF): Areas 17 and 18
A16IO (DE): Areas 15 and 16
A14IO (DD): Areas 13 and 14
A12IO (DC): Areas 11 and 12
A8IO (DA): Areas 7 and 8
A6IO (D9): Area 6
A5IO (D8): Areas 4 and 5
Exclusive Signals for Areas
Areas can be accessed using the exclusive signals (address strobe and read signals) as well as the common control signals.
To use these exclusive signals, they should be configured using G/A read signal control register (0x48138).
The AxxAS bit is used to enable/disable the address strobe signal, and the AxxRD bit is used to enable/disable the read signal. When "1" is written to the bit, the exclusive signal for the corresponding area(s) is enabled and when "0" is written, it is disabled (disabled by default). The bit names and the corresponding areas are as follows:
A18AS (DF), A18RD (D7): | Areas 17 and 18 |
A16AS (DE), A16RD (D6): | Areas 15 and 16 |
A14AS (DD), A14RD (D5): | Areas 13 and 14 |
A12AS (DC), A12RD (D4): | Areas 11 and 12 |
A8AS (DA), A8RD (D2): | Areas 7 and 8 |
A6AS (D9), A6RD (D1): | Area 6 |
A5AS (D8), A5RD (D0): | Areas 4 and 5 |
#CE selected with AxxAS (ORed) |
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#WRH |
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| #GAAS |
| P21 |
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#WRL |
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#RD |
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| #GARD |
| P31 |
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#CE selected with AxxRD (ORed) |
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Figure 4.3 #GAAS and #GARD Signals
The address strobe signal and the read signal are output from the P21 pin and P31 pin, respectively. Therefore, when using these signals, the pin(s) must be configured for exclusive signal output using the port function select register and port function extension register.
To output the exclusive address strobe signal #GAAS:
CFEX2 (D2)/Port function extension register (0x402DF) = "1"
To output the exclusive address strobe signal #GARD:
CFEX3 (D3)/Port function extension register (0x402DF) = "1"
These signals are common used to all the above areas, so when two or more areas are selected to output the exclusive signal, OR condition is applied.
BCU
S1C33L03 FUNCTION PART | EPSON |