SAB80515 Datasheet, PDF (35/270 Pages) Siemens Semiconductor Group – 8-Bit Single-Chip Microcontroller Family

On-Chip Peripheral Components
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On-Chip Peripheral Components
This chapter gives detailed information about all on-chip peripherals of the SAB 80(C)515 except
for the integrated interrupt controller, which is described separately in chapter 8. Sections 7.1 and
7.2 are associated with the general parallel and serial I/O facilities while the remaining sections
describe the miscellaneous functions such as the timers, serial interface, A/D converter, power
saving modes, watchdog timer, oscillator and clock circuitries, and system clock output.
7.1 Parallel I/O
7.1.1 Port Structures
Digital I/O
The SAB 80(C)515 allows for digital I/O on 48 lines grouped into 6 bidirectional 8-bit ports. Each
port bit consists of a latch, an output driver and an input buffer. Read and write accesses to the I/O
ports P0 through P5 are performed via their corresponding special function registers P0 to P5.
The output drivers of port 0 and 2 and the input buffers of port 0 are also used for accessing external
memory. In this application, port 0 outputs the low byte of the external memory address, time-
multiplexed with the byte being written or read. Port 2 outputs the high byte of the external memory
address when the address is 16 bits wide. Otherwise, the port 2 pins continue emitting the P2 SFR
contents (see also chapter 7.1.2 and chapter 5 for more details about the external bus interface).
Digital/Analog Input Ports
The analog input lines AN0 to AN7 of the MYMOS versions can only be used as analog inputs.
In the ACMOS versions these lines may also be used as digital inputs. In this case they are
addressed as an additional input port (port 6) via special function register P6 (0DBH). Since port 6
has no internal latch, the contents of SFR P6 only depends on the levels applied to the input lines.
When used as analog input the required analog channel is selected by a three-bit field in SFR
ADCON , as described in section 7.4. Of course, it makes no sense to output a value to these input-
only ports by writing to the SFR P6 or P8; this will have no effect.
Semiconductor Group
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