MC68HC705JJ7 Datasheet, PDF (100/164 Pages) Freescale Semiconductor, Inc – Microcontrollers

Simple Synchronous Serial Interface
9.3.3 SIOP Data Register
The SIOP data register (SDR) is located at address $000C and serves as both the transmit and receive
data register. Writing to this register will initiate a message transmission if the node is in master mode.
The SIOP subsystem is not double buffered and any write to this register will destroy the previous
contents. The SDR can be read at any time. However, if a transfer is in progress the results may be
ambiguous. Writing to the SDR while a transfer is in progress can cause invalid data to be transmitted
and/or received. Figure 9-6 shows the position of each bit in the register. This register is not affected by
reset.
Address: $000C
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Bit 7
6
5
4
3
2
1
Bit 0
Write:
Reset:
Unaffected by reset
Figure 9-6. SIOP Data Register (SDR)
MC68HC705JJ7 • MC68HC705JP7 Advance Information Data Sheet, Rev. 4.1
100
Freescale Semiconductor