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參數(shù)資料
| 型號： | HF88M08 |
| 廠商： | King Billion Electronics Co., Ltd. |
| 英文描述： | 512K x 8 bit Mask ROM |
| 中文描述： | 為512k × 8位掩模ROM |
| 文件頁數(shù)： | 9/19頁 |
| 文件大?。?/td> | 320K |
| 代理商： | HF88M08 |
King Billion Electronics Co., Ltd
駿 億 電 子 股 份 有 限 公 司
HF88M08
from/to expansion I/O registers (P0, P1, DIR0, DIR1). This design is useful in certain application
scenarios where in the midst of the multi-byte address loading process, an interrupt to the MCU main
loop occurs. And in the interrupt service routine, manipulation of expansion I/O registers is performed,
i.e., key board is scanned using P0 and P1. When the execution of program returns to main loop after
interrupt service routine completed, the loading of address can still resume from where it was interrupted.
January 16, 2004
This specification is subject to change without notice. Please contact sales person for the latest version before use.
Page 9 of 19
V1.11
6.3
Sequential Read Mode and Auto Increment of Address Counter
With each read access to the ROM data (RS = “0xx”), the Address Counter is incremented automatically
by one with rising edge of OEn to facility sequential access to a block of ROM data and avoid repeated
loading of addresses.
6.4
Output data to External I/O
The device’s 16-bit Expansion I/O capability provides additional I/O ports for applications where the I/O
pin are heavily used. To use as a certain pin as output pin, the corresponding bit in Direction Register
must be set to ‘1’. Please refer to the following example where output 0x00 to P0 to ‘0’ is intended.
1.
Set RS to “101” (DIR0).
2.
Keep D7 ~ D0 at 0xff (all bits in output mode).
3.
Pulse the WEn to low then high to write to write contents of D-bus to DIR0.
4.
Set RS to “100” (P0 Output Register).
5.
Set D7 ~ D0 to 0x00.
6.
Pulse the WEn to low then high to write contents of D-bus to P0 and drive all bits in P0 to low.
6.5
Reading Input pin status
To use expansion I/O ports as input pins and read the status from them, the corresponding bit in direction
register must be set to ‘0’. Please see the following example where reading inputs from of P1 is
intended.
1.
Set RS to “111” (DIR1).
2.
Set D7 ~ D0 to 0x00.
3.
Pulse the WEn to low then high to set DIR1 to all High-Impedance input mode.
4.
Set RS to “110” (P1 Output Register).
5.
Pulse the OEn to low.
6.
Read P1 then set the OEn back to high.
There is one thing should be noted. For any unused (open) expansion I/O pin, it is advisable to set the
port to output mode either at ‘0’ or ‘1’ state to prevent it from floating or fix it at VDD or VSS if it is set
to input mode. Otherwise, the noise might cause the unnecessary power consumption.
6.6
Retrieving the Contents of Expansion I/O registers
The contents of all four registers can be read through data bus. The ability to access the contents of
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