mc68hc05p18a Freescale Semiconductor, Inc, mc68hc05p18a Datasheet - Page 83

• Manufacturer Part Number: mc68hc05p18a
• Description: Mc68hc05p18a Hcmos Microcontroller Unit
• Manufacturer: Freescale Semiconductor, Inc

9.4.3 SIOP Data Register
MC68HC05P18A
Address:
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
not affected by reset.
Reset:
Read:
Write:
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$000C
Bit 7
SD7
Serial Input/Output Ports (SIOP)
shows the position of each bit in the register. This register is
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Figure 9-5. SIOP Data Register (SDR)
SD6
6
SD5
5
Unaffected by reset
SD4
4
SD3
3
Serial Input/Output Ports (SIOP)
SD2
2
SD1
SIOP Registers
1
Technical Data
Bit 0
SD0