Maxim Integrated MAXQ7667 - Manual (Page 35)

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MAXQ7667 User’s Guide
The Accumulator Pointer Control Register (APC) controls the automatic-increment/decrement mode as well as selects the range of bits
(modulo) in the AP register that will be incremented or decremented. There are nine different unique settings for the APC register, as
listed in Table 3-1.
Table 3-1. Accumulator Pointer Control Register Settings
For the modulo increment or decrement operation, the selected range of bits in AP are incremented or decremented. However, if these
bits roll over or under, they simply wrap around without affecting the remaining bits in the accumulator pointer. So, the operations can
be defined as follows:
• Increment modulo 2: AP = AP[3:1] + ((AP[0] + 1) mod 2)
• Decrement modulo 2: AP = AP[3:1] + ((AP[0] - 1) mod 2)
• Increment modulo 4: AP = AP[3:2] + ((AP[1:0] + 1) mod 4)
• Decrement modulo 4: AP = AP[3:2] + ((AP[1:0] - 1) mod 4)
• Increment modulo 8: AP = AP[3] + ((AP[2:0] + 1) mod 8)
• Decrement modulo 8: AP = AP[3] + ((AP[2:0] - 1) mod 8)
• Increment modulo 16: AP = (AP + 1) mod 16
• Decrement modulo 16: AP = (AP - 1) mod 16
For this example, assume that all 16 accumulator registers are initially set to zero.
move AP, #02h ; select A[2] as active accumulator
move APC, #02h ; auto-increment AP[1:0] modulo 4
; AP A[0] A[1] A[2] A[3]
; 02 0000 0000 0000 0000
add #01h ; 03 0000 0000 0001 0000
add #02h ; 00 0000 0000 0001 0002
add #03h ; 01 0003 0000 0001 0002
add #04h ; 02 0003 0004 0001 0002
add #05h ; 03 0003 0004 0006 0002
APC.2
(MOD2)
APC.1
(MOD1)
APC.0
(MOD0)
APC.6
(IDS)
APC AUTO INCREMENT/DECREMENT SETTING
0 0 0 X 00h No autoincrement/decrement (default mode)
0 0 1 0 01h Increment bit 0 of AP (modulo 2)
0 0 1 1 41h Decrement bit 0 of AP (modulo 2)
0 1 0 0 02h Increment bits [1:0] of AP (modulo 4)
0 1 0 1 42h Decrement bits [1:0] of AP (modulo 4)
0 1 1 0 03h Increment bits [2:0] of AP (modulo 8)
0 1 1 1 43h Decrement bits [2:0] of AP (modulo 8)
1 0 0 0 04h Increment all 4 bits of AP (modulo 16)
1 0 0 1 44h Decrement all 4 bits of AP (modulo 16)