TS80C51RA2 Atmel Corporation, TS80C51RA2 Datasheet - Page 35

• Manufacturer Part Number: TS80C51RA2
• Description: High Performance 8-bit Microcontroller
• Manufacturer: Atmel Corporation

Broadcast Address
4188A–8051–10/02
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 1; for slaves B and C, bit 1 is a don’t care bit. To communicate with
slaves B and C, but not slave A, 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:
For slaves A and B, bit 2 is a don’t care bit; for slave C, bit 2 is set. To communicate with
all of the slaves, the master must send an address FFh. To communicate with slaves A
and B, but not slave C, the master can send and address FBh.
Slave A:SADDR1111 0001b
Slave B:SADDR1111 0011b
Slave C:SADDR=1111 0010b
Broadcast =SADDR OR SADEN1111 111Xb
SADDR0101 0110b
SADEN1111 1100b
SADEN1111 1010b
Broadcast1111 1X11b,
SADEN1111 1001b
Broadcast1111 1X11B,
SADEN1111 1101b
Broadcast1111 1111b
TS8xC51Rx2
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