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SA-1110 Developer’s Manual 297
Peripheral Control Module
Note: A question mark (?) signifies that the Reset value of that bit is undefined when the processor has
completed its reset cycle.
11.9.3 GPCLK Control Register 1
GPCLK Control Register 1 (GPCLKR1) contains one bit field that controls the general purpose
clock.
11.9.3.1 Transmit Enable (TXE)
The Transmit Enable bit enables and disables the GPCLK. When TXE=0, the GPCLK transmitter
logic is disabled. The clocks are turned off to save power.
When TXE=1, the GPCLK transmitter logic is enabled
Note: You must first program all other control bits before setting the TXE bit.
The following table shows the location of the TXE bit within GPCLK Control Register 1. The TXE
bit is reset to a known state to ensure the GPCLK is disabled following a reset of the SA-1110. All
other bits shown in the table are reserved for future use.
Address: 0h 8002 0060 GPCLKR0 Read/Write
Bit 7 6 5 4 3 2 1 0
Reserved Reserved SCD SCE Reserved Reserved Reserved SUS
Reset ? ? ? ? ? ? ? 0
Bit Name Description
0SUS
GPCLK/UART select.
0 – GPCLK mode selected.
1 – UART mode selected.
Note: For SUS=0, TXD1 and RXD1 control is given to the PPC unit. If UPR is set in
the PPC unit, SUS is ignored, the UART uses GPIO<14> to transmit and GPIO<15>
to receive data, and serial port 1 defaults to GPLCK mode. The user must also
program the GAFR and GPDR registers appropriately in the GPIO unit.
1 Reserved
Reserved for Future Expansion.
2 Reserved
Reserved for Future Expansion.
3 Reserved
Reserved for Future Expansion.
4SCE
Sample clock enable.
0 – Sample clock disabled.
1 – Sample clock enabled.
5SCD
Sample clock direction.
0 – If sample clock enabled, it is input on GPIO pin 16 and is not used.
1 – The sample clock which is generated within the GPCLK unit (the clock that is output
after dividing the 3.6864 MHz reference by the programmable BRD field), is output to the
GPIO pin 16 in the frequency range of 900 Hz – 3.6864MHz..
6 Reserved
Reserved for Future Expansion.
7 Reserved
Reserved for Future Expansion.