MCS51 - lecture 6

Lecture 6 1/32 Extending MCS51 system Built-in peripherals MCS51 family

MCS51 - system extending 2/32 Designer of MCS51 system should remember about: multiplexed data D0..D7 bus and address lines A0..A7 on P0 port, so external 8-bit latch for lower address byte is needed; load capacity of port outputs; the absence dedicated control signal for external devices (it means common external peripherals and data memory address space); separate address spaces of external programme and data memories; big number of MCS51 family members, which differentiate in capacity of built-in memories and devices.

MCS51 - system extending 3/32 Connecting with external memories:

MCS51 - system extending 4/32 Connecting with peripherals of 8085 series :

MCS51 - system extending 5/32 Connecting with peripherals of 8080 series:

MCS51 - system extending 6/32 Connecting with peripherals of 8080 series (another solution):

MCS51 - built-in peripherals 7/32 Synchronized bidirectional parallel port: additional port with 4 hand-shake signals can work without handshake (like standard P0..P3).

MCS51 - built-in peripherals 8/32 Synchronized port - basic timings data input data output

MCS51 - built-in peripherals 9/32 UPI - Universal Peripheral Interface: based on P0 with additional registers; microcontroller acts as programmable control unit of peripheral device; supervising system considers P0 as double bidirectional port; additional signals: /RD, /WR, /CS (P2.5) i A0 (P2.4); /CS=0 enables UPI for data exchange; A0=0 selects data buffer/register, A0=1 selects control/status register.

Virtual parallel ports: up-to over ten parallel ports; accessible like standard built-in ports; some of ports have directly-addressed bits. MCS51 - built-in peripherals 10/32

MCS51 - built-in peripherals 11/32 PWM outputs f PWM = f OSC : 2 : 255 : (1+PWMP)

MCS51 - built-in peripherals 12/32 Analog comparators Atmel 89C1051, 89C2051:

MCS51 - built-in peripherals 13/32 Analog comparators Philips

MCS51 - built-in peripherals 14/32 Intel A/D converters

MCS51 - built-in peripherals 15/32 Philips A/D converters: 8/10b successive approximation; t CONW = m.c.; conversion start by hardware else software; possible interrupt request; latches for conversion results.

MCS51 - built-in peripherals 16/32 Siemens A/D converters: programmable upper and lower conversion range limits.

MCS51 - built-in peripherals 17/32 Arithmetic units Siemens MDU: shifting, normalization, division and multiplication 16b i 32b NB numbers; calculation time reduced several times (to 4..6 m.c.); accessible via 6 data registers (MD0..MD5) and control register (ARCON); type of operation depends on the sequence of writings to MDx registers. Philips arithmetic units: hardware division 24b / 8b numbers in 8 m.c.; hardware division or multiplication 24b by 16b numbers in 4 m.c.

MCS51 - built-in peripherals 18/32 XRAM memory: from hundreds to thousands bytes; accessible like true external RAM; usage MOVX operation with R0 i R1 addressing depends on implementation; active all the time after reset either activated by special control bit;

MCS51 - built-in peripherals 19/32 EEPROM memory: from hundreds to thousands bytes; accessible via special registers: address, data & control/state; reading immediate; writing time up to several ms; initialisation of writing needs special control sequence.

MCS51 - built-in peripherals 20/32 Watchdogs: overflowing watchdog counter causes microcontroller reset; counter reset needs special software sequence. Siemens watchdog

MCS51 - built-in peripherals 21/32 Watchdogs - cont. Philips watchdog

MCS51 - built-in peripherals 22/32 Oscillator watchdogs: supervise the main clock generator; own, separate oscillator; when main clock frequency falls, they resets microcontroller. Supply voltage supervisors: detect supply voltage falls below any limit value (exmp. below 4,5V from 5V); detected falls cause set special flag in SFR; can cause interrupt request of highest priority else reset.

MCS51 - built-in peripherals 23/32 RTC units: additional oscillator 32768Hz; set of dividers and registers for: seconds, minutes, hours, week days, days (also months, years); possible alert functions and interrupt requests. Seconds timer: counts pulses of frequency f=32768Hz; interrupt request period T=1s; can run also in power down mode of microcontroller.

MCS51 - family 24/32

MCS51 - zestawienie 25/32

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