AT89C51AC3 Atmel Corporation, AT89C51AC3 Datasheet - Page 62

• Manufacturer Part Number: AT89C51AC3
• Manufacturer: Atmel Corporation

Specifications of AT89C51AC3

• Flash (kbytes): 64 Kbytes
• Max. Operating Frequency: 60 MHz
• Cpu: 8051-12C
• Max I/o Pins: 32
• Spi: 1
• Uart: 1
• Adc Channels: 8
• Adc Resolution (bits): 10
• Adc Speed (ksps): 62.5
• Sram (kbytes): 2.25
• Eeprom (bytes): 2048
• Self Program Memory: API
• Operating Voltage (vcc): 3.0 to 5.5
• Timers: 4
• Isp: UART
• Watchdog: Yes

62
Given Address
Broadcast Address
AT89C51AC3
Each device has an individual address that is specified in the SADDR register; the
SADEN register is a mask byte that contains don’t-care bits (defined by zeros) to form
the device’s given address. The don’t-care bits provide the flexibility to address one or
more slaves at a time. The following example illustrates how a given address is formed.
To address a device by its individual address, the SADEN mask byte must be 1111
1111b.
For example:
Here is an example of how to use given addresses to address different slaves:
The SADEN byte is selected so that each slave may be addressed separately.
For slave A, bit 0 (the LSB) is a don’t-care bit; for slaves B and C, bit 0 is a 1. To com-
municate with slave A only, the master must send an address where bit 0 is clear (e.g.
1111 0000b).
For slave A, bit 1 is a 0; for slaves B and C, bit 1 is a don’t care bit. To communicate with
slaves A and B, but not slave C, the master must send an address with bits 0 and 1 both
set (e.g. 1111 0011b).
To communicate with slaves A, B and C, the master must send an address with bit 0 set,
bit 1 clear, and bit 2 clear (e.g. 1111 0001b).
A broadcast address is formed from the logical OR of the SADDR and SADEN registers
with zeros defined as don’t-care bits, e.g.:
The use of don’t-care bits provides flexibility in defining the broadcast address, however
in most applications, a broadcast address is FFh. The following is an example of using
broadcast addresses:
Slave A:SADDR1111 0001b
Slave B:SADDR1111 0011b
Slave C:SADDR1111 0011b
Slave A:SADDR1111 0001b
Slave B:SADDR1111 0011b
Slave C:SADDR=1111 0010b
SADDR0101 0110b
SADEN1111 1100b
Given0101 01XXb
SADEN1111 1010b
Given1111 0X0Xb
SADEN1111 1001b
Given1111 0XX1b
SADEN1111 1101b
Given1111 00X1b
SADDR0101 0110b
SADEN1111 1100b
SADDR OR SADEN1111 111Xb
SADEN1111 1010b
Given1111 1X11b,
SADEN1111 1001b
Given1111 1X11B,
SADEN1111 1101b
Given1111 1111b
4383D–8051–02/08