TS80C52X2
6.4.3 Given Address
Each device has an individual address that is specified in 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:
SADDR
SADEN
Given
0101 0110b
1111 1100b
0101 01XXb
The following is an example of how to use given addresses to address different slaves:
Slave A:
Slave B:
Slave C:
SADDR
SADEN
Given
1111 0001b
1111 1010b
1111 0X0Xb
SADDR
SADEN
Given
1111 0011b
1111 1001b
1111 0XX1b
SADDR
SADEN
Given
1111 0010b
1111 1101b
1111 00X1b
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 communicate 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).
6.4.4 Broadcast Address
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.:
SADDR
0101 0110b
1111 1100b
1111 111Xb
SADEN
Broadcast =SADDR OR SADEN
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:
Slave B:
Slave C:
SADDR
1111 0001b
SADEN
1111 1010b
Broadcast 1111 1X11b,
SADDR
SADEN
1111 0011b
1111 1001b
Broadcast 1111 1X11B,
SADDR=
SADEN
Broadcast 1111 1111b
1111 0010b
1111 1101b
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.
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Rev. B - Jan. 25, 1999
Preliminary
TEMIC [ TEMIC SEMICONDUCTORS ]
