參數(shù)資料
型號(hào): μPD784036(A)
廠商: NEC Corp.
英文描述: 8/16 Bit Single Chip Microcontrollers(8/16 位單片微控制器)
中文描述: 8 / 16位單片機(jī)微控制器(8 / 16位單片微控制器)
文件頁數(shù): 51/90頁
文件大小: 402K
代理商: ΜPD784036(A)
μ
PD784035(A), 784036(A)
51
9.3 Programmable Wait
When the memory space is divided into eight spaces, a wait state can be separately inserted for each memory
space while the RD or WR signal is active. This prevents the overall system efficiency from being degraded even
when memory devices having different access times are connected.
In addition, an address wait function that extends the ASTB signal active period is provided to assure a longer
address decode time. (This function is set for the entire space.)
9.4 Pseudo-Static RAM Refresh Function
Refresh is performed as follows:
Pulse refresh
A bus cycle is inserted where a refresh pulse is output on the REFRQ pin at regular ntervals. When the memory
space is divided into eight, and a specified area is being accessed, refresh pulses can also be output on
the REFRQ pin as the memory is being accessed. This can prevent the refresh cycle from suspending normal
memory access.
Power-down self-refresh
In standby mode, a low-level signal is output on the REFRQ pin to maintain the contents of pseudo-static RAM.
9.5 Bus Hold Function
A bus hold function is provided to facilitate connection to devices such as a DMA controller. Suppose that a bus
hold request signal (HLDRQ) is received from an external bus master. In this case, upon the completion of the bus
cycle being performed at the reception, the address bus, address/data bus, ASTB, RD, and WR pins are placed in
the high-impedance state, and the bus hold acknowledge signal (HLDAK) is made active to release the bus for the
external bus master.
While the bus hold function is being used, the external wait and pseudo-static RAM refresh functions are disabled.
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