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2.5 Microcontroller Operation
2.5.1 ONCE Mode
2-14
Figure 2.7
DMA External Memory Access
ALE
WR/orRD/
AD[7:0]
Address
A[15:8]
The 80C32 microcontroller core used in the SYM53C040 is an 8-bit Intel
MCS 51 family compatible device with 256 bytes of internal scratch RAM
and no internal ROM. This microcontroller uses a shared address/data
bus and can address either 64 Kbytes of shared program and data
memory or 16 Kbytes of internal memory and 47 Kbytes each of external
program and data memory spaces. The microcontroller executes one
instruction every 12 clocks. Additional functionality includes two 16-bit
timers, a full-duplex UART, and two additional external interrupt sources
(five interrupt sources total).
For more information on the operation of the microcontroller core, refer
to documentation on the Intel MCS 51 embedded microcontroller family.
The microcontroller core has two external interrupt functions as well as
the TXD and RXD serial port functions. The user can access these
functions on the microcontroller core by setting the External Interrupt
Enable and Serial Port Enable bits in the
register (0xFF05).
ONCE mode is available for use as in any standard Intel 80C32
microcontroller. However, the DMA feature cannot be used when the
microcontroller is in ONCE mode. This is because the DMA logic inside
the SYM53C040 looks for a signal from the microcontroller to indicate
that it is halted before beginning any DMA operation. ONCE mode does
not provide this signal to the DMA logic.
Functional Description
Data/Input
Address
High Address
System Control (SYSCTRL)
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