p89lpc904 NXP Semiconductors, p89lpc904 Datasheet - Page 19

• Manufacturer Part Number: p89lpc904
• Description: 8-bit Microcontrollers With Two-clock Accelerated 80c51 Core 1 Kb 3 V Byte-erasable Flash With 8-bit A/d Converter
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 13521
Preliminary data
8.10 Memory organization
8.11 Data RAM arrangement
8.9.5 Boundary limits interrupt
8.9.6 DAC output to a port pin with high output impedance
8.9.7 Clock divider
8.9.8 Power-down and idle mode
The A/D converter has both a high and low boundary limit register. After the four
MSBs have been converted, these four bits are compared with the four MSBs of the
boundary high and low registers. If the four MSBs of the conversion are outside the
limit an interrupt will be generated, if enabled. If the conversion result is within the
limits, the boundary limits will again be compared after all 8 bits have been converted.
An interrupt will be generated, if enabled, if the result is outside the boundary limits.
The boundary limit may be disabled by clearing the boundary limit interrupt enable.
The A/D converter’s DAC block can be output to a port pin. In this mode, the
AD1DAT3 register is used to hold the value fed to the DAC. After a value has been
written to the DAC (written to AD1DAT3), the DAC output will appear on the channel 3
pin.
The A/D converter requires that its internal clock source be in the range of 500 kHz to
3.3 MHz to maintain accuracy. A programmable clock divider that divides the clock
from 1 to 8 is provided for this purpose.
In idle mode the A/D converter, if enabled, will continue to function and can cause the
device to exit idle mode when the conversion is completed if the A/D interrupt is
enabled. In Power-down mode or Total power-down mode, the A/D does not function.
If the A/D is enabled, it will consume power. Power can be reduced by disabling the
A/D.
The various P89LPC904 memory spaces are as follows:
The 128 bytes of on-chip RAM is organized as follows:
Table 5:
Type
DATA
•
•
•
DATA
128 bytes of internal data memory space (00h:7Fh) accessed via direct or indirect
addressing, using instruction other than MOVX and MOVC. All or part of the Stack
may be in this area.
SFR
Special Function Registers. Selected CPU registers and peripheral control and
status registers, accessible only via direct addressing.
CODE
64 kB of Code memory space, accessed as part of program execution and via the
MOVC instruction. The P89LPC904 has 1 kB of on-chip Code memory.
On-chip data memory usages
Data RAM
Memory that can be addressed directly and indirectly 128
Rev. 02 — 25 June 2004
8-bit microcontrollers with two-clock accelerated 80C51 core
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
P89LPC904
Size (Bytes)
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