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SST89E516RD2-40-C-NJE 参数 Datasheet PDF下载

SST89E516RD2-40-C-NJE图片预览
型号: SST89E516RD2-40-C-NJE
PDF下载: 下载PDF文件 查看货源
内容描述: FlashFlex MCU [FlashFlex MCU]
分类和应用: 外围集成电路微控制器PC时钟
文件页数/大小: 81 页 / 832 K
品牌: SST [ SILICON STORAGE TECHNOLOGY, INC ]
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FlashFlex MCU  
SST89E516RD2 / SST89E516RD  
SST89V516RD2 / SST89V516RD  
Data Sheet  
6.1.2 Automatic Address Recognition  
Slave 2  
Automatic Address Recognition helps to reduce the MCU  
time and power required to talk to multiple serial devices.  
Each device is hooked together sharing the same serial  
link with its own address. In this configuration, a device is  
only interrupted when it receives its own address, thus  
eliminating the software overhead to compare addresses.  
SADDR  
SADEN  
GIVEN  
=
=
=
1111 0011  
1111 1001  
1111 0XX1  
6.1.2.1 Using the Given Address to Select Slaves  
Any bits masked off by a 0 from SADEN become a “don’t  
care” bit for the given address. Any bit masked off by a 1,  
becomes ANDED with SADDR. The “don’t cares” provide  
flexibility in the user-defined addresses to address more  
slaves when using the given address.  
This same feature helps to save power because it can be  
used in conjunction with idle mode to reduce the system’s  
overall power consumption. Since there may be multiple  
slaves hooked up serial to one master, only one slave  
would have to be interrupted from idle mode to respond to  
the master’s transmission. Automatic Address Recognition  
(AAR) allows the other slaves to remain in idle mode while  
only one is interrupted. By limiting the number of interrup-  
tions, the total current draw on the system is reduced.  
Shown in the example above, Slave 1 has been given an  
address of 1111 0001 (SADDR). The SADEN byte has  
been used to mask off bits to a given address to allow more  
combinations of selecting Slave 1 and Slave 2. In this case  
for the given addresses, the last bit (LSB) of Slave 1 is a  
“don’t care” and the last bit of Slave 2 is a 1. To communi-  
cate with Slave 1 and Slave 2, the master would need to  
send an address with the last bit equal to 1 (e.g. 1111  
0001) since Slave 1’s last bit is a don’t care and Slave 2’s  
last bit has to be a 1. To communicate with Slave 1 alone,  
the master would send an address with the last bit equal to  
0 (e.g. 1111 0000), since Slave 2’s last bit is a 1. See the  
table below for other possible combinations.  
There are two ways to communicate with slaves: a group of  
them at once, or all of them at once. To communicate with a  
group of slaves, the master sends out an address called  
the given address. To communicate with all the slaves, the  
master sends out an address called the “broadcast”  
address.  
AAR can be configured as mode 2 or 3 (9-bit modes) and  
setting the SM2 bit in SCON. Each slave has its own SM2  
bit set waiting for an address byte (9th bit = 1). The Receive  
Interrupt (RI) flag will only be set when the received byte  
matches either the given address or the broadcast  
address. Next, the slave then clears its SM2 bit to enable  
reception of the data bytes (9th bit = 0) from the master.  
When the 9th bit = 1, the master is sending an address.  
When the 9th bit = 0, the master is sending actual data.  
Select Slave 1 Only  
Slave 1  
Given Address  
Possible Addresses  
1111 0X0X  
1111 0000  
1111 0100  
If mode 1 is used, the stop bit takes the place of the 9th bit.  
Bit RI is set only when the received command frame  
address matches the device’s address and is terminated  
by a valid stop bit. Note that mode 0 cannot be used. Set-  
ting SM2 bit in the SCON register in mode 0 will have no  
effect.  
Select Slave 2 Only  
Slave 2  
Given Address  
Possible Addresses  
1111 0XX1  
1111 0111  
1111 0011  
Select Slaves 1 & 2  
Each slave’s individual address is specified by SFR  
SADDR. SFR SADEN is a mask byte that defines “don’t  
care” bits to form the given address when combined with  
SADDR. See the example below:  
Slaves 1 & 2  
Possible Addresses  
1111 0001  
1111 0101  
If the user added a third slave such as the example below:  
Slave 1  
SADDR  
SADEN  
GIVEN  
=
=
=
1111 0001  
1111 1010  
1111 0X0X  
Slave 3  
SADDR = 1111 1001  
SADEN = 1111 0101  
GIVEN  
= 1111 X0X1  
©2007 Silicon Storage Technology, Inc.  
S71273-03-000  
1/07  
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