MC68HC05P18A Datasheet, PDF (83/130 Pages) Freescale Semiconductor, Inc – HCMOS Microcontroller Unit

Freescale Semiconductor, Inc.
Serial Input/Output Ports (SIOP)
SIOP Registers
9.4.3 SIOP Data Register
This register 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 SIOP 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 and
the DCOL bit will be set. Writing to the SDR while a transfer is in
progress can cause invalid data to be transmitted and/or received.
Figure 9-5 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:
SD7
SD6
SD5
SD4
SD3
SD2
SD1
SD0
Write:
Reset:
Unaffected by reset
Figure 9-5. SIOP Data Register (SDR)
MC68HC05P18A
Serial Input/Output Ports (SIOP)
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Technical Data