UM10310_1 © NXP B.V. 2008. All rights reserved.
User manual Rev. 01 — 1 December 2008 34 of 139
NXP Semiconductors UM10310
P89LPC9321 User manual

For correct activation of Brownout Detect, certain VDD rise and fall times must be

observed. Please see the data sheet for specifications.

5.2 Power-on detection

The Power-On Detect has a function similar to the Brownout Detect, but is designed to

work as power initially comes up, before the power supply voltage reaches a level where

the Brownout Detect can function. The POF flag (RSTSRC.4) is set to indicate an initial

power-on condition. The POF flag will remain set until cleared by software by writing a

logic 0 to the bit. BOF (RSTSRC.5) will be set when POF is set.

5.3 Power reduction modes

The P89LPC9321 supports three different power reduction modes as determined by SFR

bits PCON[1:0] (see Table17).

Table 15. BOD Trip points configuration
BOE1
(UCFG1.5) BOE0
(UCFG1.3) BOICFG1
(BOICFG.1) BOICFG0
(BOICFG.0) BOD Reset BOD
Interrupt
00 0 0 Reserved
00 0 1
00 1 0
00 1 1
01 0 0
0 1 0 1 2.2V 2.4V
0 1 1 0 2.2V 2.6V
0 1 1 1 2.2V 3.2V
10 0 0 Reserved
10 0 1
1 0 1 0 2.4V 2.6V
1 0 1 1 2.4V 3.2V
11 0 0 Reserved
11 0 1
11 1 0
1 1 1 1 3.0V 3.2V
Table 16. BOD Reset and BOD Interrupt configuration
PMOD1/PMOD0(PCON[1:0]) BOI
(PCON.4)
EBO
(IEN0.5)
EA
(IEN0.7)
BOD
Reset
BOD
Interrupt
11 (total power-down) X X X N N
11 (any mode other than total
power down) 0XXYN
10XYN
X0YN
11YY